US20060202616A1 - Multilayer polymer light-emitting diodes for solid state lighting applications - Google Patents
Multilayer polymer light-emitting diodes for solid state lighting applications Download PDFInfo
- Publication number
- US20060202616A1 US20060202616A1 US11/366,186 US36618606A US2006202616A1 US 20060202616 A1 US20060202616 A1 US 20060202616A1 US 36618606 A US36618606 A US 36618606A US 2006202616 A1 US2006202616 A1 US 2006202616A1
- Authority
- US
- United States
- Prior art keywords
- layer
- light
- emitting device
- polymer
- solvent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 229920000642 polymer Polymers 0.000 title claims abstract description 59
- 239000007787 solid Substances 0.000 title claims abstract description 17
- 238000002347 injection Methods 0.000 claims abstract description 77
- 239000007924 injection Substances 0.000 claims abstract description 77
- 239000000243 solution Substances 0.000 claims abstract description 51
- 238000000034 method Methods 0.000 claims abstract description 23
- 239000002798 polar solvent Substances 0.000 claims abstract description 14
- 238000009877 rendering Methods 0.000 claims abstract description 11
- 239000012454 non-polar solvent Substances 0.000 claims abstract description 8
- 239000010410 layer Substances 0.000 claims description 217
- 239000002904 solvent Substances 0.000 claims description 40
- 230000005525 hole transport Effects 0.000 claims description 22
- 238000004770 highest occupied molecular orbital Methods 0.000 claims description 16
- 238000004768 lowest unoccupied molecular orbital Methods 0.000 claims description 15
- 229920000620 organic polymer Polymers 0.000 claims description 12
- 238000001704 evaporation Methods 0.000 claims description 6
- 229930195733 hydrocarbon Natural products 0.000 claims description 5
- 150000002430 hydrocarbons Chemical class 0.000 claims description 5
- 239000000758 substrate Substances 0.000 claims description 5
- 239000004215 Carbon black (E152) Substances 0.000 claims description 4
- 229920000547 conjugated polymer Polymers 0.000 claims description 4
- 230000006872 improvement Effects 0.000 claims description 4
- 238000010129 solution processing Methods 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 2
- 238000001429 visible spectrum Methods 0.000 claims description 2
- 239000011241 protective layer Substances 0.000 claims 1
- 125000002524 organometallic group Chemical group 0.000 abstract description 12
- 238000012545 processing Methods 0.000 abstract description 9
- 238000005286 illumination Methods 0.000 abstract description 5
- 238000005530 etching Methods 0.000 abstract description 4
- 239000004973 liquid crystal related substance Substances 0.000 abstract description 4
- 230000003993 interaction Effects 0.000 abstract description 2
- 239000011734 sodium Substances 0.000 description 38
- -1 poly(9,9-dioctylfluorene) Polymers 0.000 description 31
- 239000000463 material Substances 0.000 description 28
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 24
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 15
- 229910006145 SO3Li Inorganic materials 0.000 description 14
- 229920000144 PEDOT:PSS Polymers 0.000 description 13
- 238000004519 manufacturing process Methods 0.000 description 13
- 239000000203 mixture Substances 0.000 description 12
- 229910052741 iridium Inorganic materials 0.000 description 11
- 229910052751 metal Inorganic materials 0.000 description 10
- 239000002184 metal Substances 0.000 description 10
- 229920000291 Poly(9,9-dioctylfluorene) Polymers 0.000 description 9
- 230000015572 biosynthetic process Effects 0.000 description 9
- 238000002161 passivation Methods 0.000 description 9
- 229920003227 poly(N-vinyl carbazole) Polymers 0.000 description 9
- 238000003786 synthesis reaction Methods 0.000 description 7
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 6
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 description 6
- YLQWCDOCJODRMT-UHFFFAOYSA-N fluoren-9-one Chemical compound C1=CC=C2C(=O)C3=CC=CC=C3C2=C1 YLQWCDOCJODRMT-UHFFFAOYSA-N 0.000 description 6
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 6
- 238000001228 spectrum Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- RICKKZXCGCSLIU-UHFFFAOYSA-N 2-[2-[carboxymethyl-[[3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl]methyl]amino]ethyl-[[3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl]methyl]amino]acetic acid Chemical compound CC1=NC=C(CO)C(CN(CCN(CC(O)=O)CC=2C(=C(C)N=CC=2CO)O)CC(O)=O)=C1O RICKKZXCGCSLIU-UHFFFAOYSA-N 0.000 description 5
- 229910052788 barium Inorganic materials 0.000 description 5
- 239000003086 colorant Substances 0.000 description 5
- 229910052709 silver Inorganic materials 0.000 description 5
- 229910052708 sodium Inorganic materials 0.000 description 5
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 4
- BZLVMXJERCGZMT-UHFFFAOYSA-N Methyl tert-butyl ether Chemical compound COC(C)(C)C BZLVMXJERCGZMT-UHFFFAOYSA-N 0.000 description 4
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 4
- 239000007983 Tris buffer Substances 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 238000005266 casting Methods 0.000 description 4
- 229910052737 gold Inorganic materials 0.000 description 4
- 239000010931 gold Substances 0.000 description 4
- 239000012299 nitrogen atmosphere Substances 0.000 description 4
- 239000012044 organic layer Substances 0.000 description 4
- 150000003384 small molecules Chemical class 0.000 description 4
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 description 3
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 3
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- 229920002521 macromolecule Polymers 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 230000005693 optoelectronics Effects 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 229920000553 poly(phenylenevinylene) Polymers 0.000 description 3
- 229920002959 polymer blend Polymers 0.000 description 3
- 239000002861 polymer material Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 description 3
- 230000006798 recombination Effects 0.000 description 3
- 238000005215 recombination Methods 0.000 description 3
- AGBXYHCHUYARJY-UHFFFAOYSA-N 2-phenylethenesulfonic acid Chemical compound OS(=O)(=O)C=CC1=CC=CC=C1 AGBXYHCHUYARJY-UHFFFAOYSA-N 0.000 description 2
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 description 2
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 2
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 description 2
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 2
- 229920001609 Poly(3,4-ethylenedioxythiophene) Polymers 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 238000013459 approach Methods 0.000 description 2
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000007639 printing Methods 0.000 description 2
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical class CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- 239000002356 single layer Substances 0.000 description 2
- 239000002195 soluble material Substances 0.000 description 2
- 238000006277 sulfonation reaction Methods 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 238000007740 vapor deposition Methods 0.000 description 2
- OHWIQIVPGPMWHV-UHFFFAOYSA-N 1,2-dihexyl-9h-fluorene Chemical compound C1=CC=C2C3=CC=C(CCCCCC)C(CCCCCC)=C3CC2=C1 OHWIQIVPGPMWHV-UHFFFAOYSA-N 0.000 description 1
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 description 1
- JIQHUXORNJIRGL-UHFFFAOYSA-N 9,9-dihexylfluorene;pyridine Chemical compound C1=CC=NC=C1.C1=CC=C2C(CCCCCC)(CCCCCC)C3=CC=CC=C3C2=C1 JIQHUXORNJIRGL-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 1
- 229910006069 SO3H Inorganic materials 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 229910052771 Terbium Inorganic materials 0.000 description 1
- 229910052776 Thorium Inorganic materials 0.000 description 1
- 229920000109 alkoxy-substituted poly(p-phenylene vinylene) Polymers 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000005234 chemical deposition Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000002508 contact lithography Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000001066 destructive effect Effects 0.000 description 1
- SBZXBUIDTXKZTM-UHFFFAOYSA-N diglyme Chemical compound COCCOCCOC SBZXBUIDTXKZTM-UHFFFAOYSA-N 0.000 description 1
- UXGNZZKBCMGWAZ-UHFFFAOYSA-N dimethylformamide dmf Chemical compound CN(C)C=O.CN(C)C=O UXGNZZKBCMGWAZ-UHFFFAOYSA-N 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- CETRZFQIITUQQL-UHFFFAOYSA-N dmso dimethylsulfoxide Chemical compound CS(C)=O.CS(C)=O CETRZFQIITUQQL-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000001194 electroluminescence spectrum Methods 0.000 description 1
- 238000005566 electron beam evaporation Methods 0.000 description 1
- 238000010893 electron trap Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 230000005281 excited state Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 229920002457 flexible plastic Polymers 0.000 description 1
- 235000011187 glycerol Nutrition 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- IVPZJRKMZLRFIL-UHFFFAOYSA-N iridium;pyridine Chemical compound [Ir].C1=CC=NC=C1 IVPZJRKMZLRFIL-UHFFFAOYSA-N 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 238000001755 magnetron sputter deposition Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000010128 melt processing Methods 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 229910052976 metal sulfide Inorganic materials 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 229920000172 poly(styrenesulfonic acid) Polymers 0.000 description 1
- 238000010094 polymer processing Methods 0.000 description 1
- 239000013047 polymeric layer Substances 0.000 description 1
- 238000001552 radio frequency sputter deposition Methods 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000011550 stock solution Substances 0.000 description 1
- 125000000999 tert-butyl group Chemical group [H]C([H])([H])C(*)(C([H])([H])[H])C([H])([H])[H] 0.000 description 1
- WHRNULOCNSKMGB-UHFFFAOYSA-N tetrahydrofuran thf Chemical compound C1CCOC1.C1CCOC1 WHRNULOCNSKMGB-UHFFFAOYSA-N 0.000 description 1
- FHYUCVWDMABHHH-UHFFFAOYSA-N toluene;1,2-xylene Chemical compound CC1=CC=CC=C1.CC1=CC=CC=C1C FHYUCVWDMABHHH-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
- H10K71/10—Deposition of organic active material
- H10K71/12—Deposition of organic active material using liquid deposition, e.g. spin coating
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
- H10K50/125—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/14—Carrier transporting layers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K2101/00—Properties of the organic materials covered by group H10K85/00
- H10K2101/10—Triplet emission
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/17—Carrier injection layers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/10—Organic polymers or oligomers
- H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
- H10K85/113—Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
- H10K85/1135—Polyethylene dioxythiophene [PEDOT]; Derivatives thereof
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/10—Organic polymers or oligomers
- H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
- H10K85/115—Polyfluorene; Derivatives thereof
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/10—Organic polymers or oligomers
- H10K85/141—Organic polymers or oligomers comprising aliphatic or olefinic chains, e.g. poly N-vinylcarbazol, PVC or PTFE
- H10K85/146—Organic polymers or oligomers comprising aliphatic or olefinic chains, e.g. poly N-vinylcarbazol, PVC or PTFE poly N-vinylcarbazol; Derivatives thereof
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/10—Organic polymers or oligomers
- H10K85/151—Copolymers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/30—Coordination compounds
- H10K85/341—Transition metal complexes, e.g. Ru(II)polypyridine complexes
- H10K85/342—Transition metal complexes, e.g. Ru(II)polypyridine complexes comprising iridium
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/60—Organic compounds having low molecular weight
- H10K85/649—Aromatic compounds comprising a hetero atom
- H10K85/656—Aromatic compounds comprising a hetero atom comprising two or more different heteroatoms per ring
- H10K85/6565—Oxadiazole compounds
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S428/00—Stock material or miscellaneous articles
- Y10S428/917—Electroluminescent
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
- Y10T428/24942—Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree
Definitions
- This invention is in the field of organic polymer-based light-emitting diodes. More particularly this invention relates to multilayer polymer light-emitting diodes (PLEDs) that, in certain embodiments, emit white light that is useful for solid state lighting applications. This invention also pertains to methods for preparing these diodes.
- PLEDs polymer light-emitting diodes
- PLEDs Polymer light-emitting diodes which employ semiconducting polymers as emitting layers have been demonstrated. A wide range of colors of emission can be achieved by varying the materials present in the emitting layers. Blends of emitting polymers alone and together with organometallic emitters can be used to achieve additional color shades of emitted light including white light.
- LEDs that emit white light are of interest and potential importance for use as back lights in active matrix displays (with color filters) and because they can be used for solid state lighting [A. J. Heeger, Solid State Commu., 1998. 107,673 & Rev. Modem Phys., 2001,73, 681; B. W. D'Andrade, S. R. Forrest, Adv. Mater., 2004, 16, 1585; R. H. Friend, R. W. Gymer, A. B. Holmes, J. H. Burroughes, R. N. Marks, C. Taliani, D. D. C. Bradley, D. A. Dos Santos, J. L. Bredas, M. J. ⁇ gdlund, and. W. R.
- PLEDs fabricated with semiconducting polymers doped with organometallic emitters offer the additional promise of “plastic” electronics. Representative examples of such devices are described in U.S. application Ser. No. 10/680,084 filed Oct. 3, 2003.
- the emissive layers of PLEDs can be fabricated by casting polymers and blends from solution, thereby enabling relatively simple and low cost manufacturing processes [G. D. Müller, A. Falcou, N. Reckefuss, M. Roijhn, V. Wiederhim, P. Rudati, H. Frohne, O. Nuyken, H. Becker, K. Meerholz, Nature, 2003, 421, 829].
- the fabrication techniques most favored for producing multilayer PLEDs include the use of sputtering and various vapor deposition methods to lay down inorganic layers such as high work function metal-metal oxide contacts (electrodes) and protective metallic overlayers. Solvent deposition methods such as spin-casting or printing successive layers from solution can be used to lay down organic polymer emissive layers as well as other layers in the devices. When multiple organic layers are present there can be problems with successive layers interacting. The solvent of a later layer can dissolve or disfigure (etch) a prior layer. It is often desirable to have each layer be smooth and coherent, thus this interaction can be destructive.
- Light may be characterized by three quantities: the CIE (Commission Internationale de l'Eclairage) coordinates, the color temperature (CT) and the color rendering index (CRI).
- CIE Commission Internationale de l'Eclairage
- CT color temperature
- CRI color rendering index
- CRI values range from 0 to 100, with 100 representing true color reproduction. Fluorescent lamps have CRI ratings between 60 and 99. Though a CIU value of at least 70 may be acceptable for certain applications, a preferred white light source will have a CRI of about 80 or higher.
- the demonstration of PLEDs which emit illumination quality white light with high brightness, high efficiency, suitable CT, high CRI and stable CIE coordinates is of importance to the future of solid state lighting.
- this invention can provide multilayer polymer light-emitting diodes (PLEDs) that in certain embodiment emit white light and are useful for solid state lighting applications. More specifically, the present invention can provide multilayer white PLEDs comprising semiconducting polymers blended with organometallic emitters as a relatively nonpolar solvent-soluble emissive layer, and relatively polar solvent-soluble organic materials (polymers or small molecules) as a hole injection/transport layer (HIL/HTL) and/or as an electron injection/transport layer (EIL/ETL); all layers preferably being cast from the corresponding solutions.
- the white emission of these preferred materials of the present invention can be used for backlights in liquid crystal displays (LCDs) and for solid state lighting applications.
- the white light is emitted from the polymer blend in a single emissive layer.
- the strategy developed in this invention enables the fabrication of multilayer white emitting PLEDs by casting the emissive polymer blends, HIL/HTL, and EIL/ETL from the corresponding solutions.
- This invention also enables the relatively simple fabrication of multilayer PLEDs which emit illumination quality light in all colors from blue to red and including white light.
- the methodology presented in this invention enables the relatively simple fabrication of multilayer PLEDs which emit illumination quality white light with high brightness, high efficiency, suitable color temperature, high color rendering index, and stable CIE (Commission Internationale de l'Eclairage) coordinates.
- the method for fabrication of multilayer PLEDs presented in this invention can be used for large-area multilayer displays and other large-area multilayer opto-electronic devices fabricated by casting the various layers from solution.
- the devices of the present invention employ an emissive layer and at least one of a hole injection/transport layer (HIL/HTL) and an electron injection/transport layer (EIL/ETL) adjacent to the emissive layer.
- HIL/HTL hole injection/transport layer
- EIL/ETL electron injection/transport layer
- the benefits of the transport layers can be observed in devices which employ a single layer hole injection anode, in which case the hole transport layer may at times be referred to as a “hole injection/transport layer” or “HIL/HTL.” and also in devices which employ a bilayer anode with the second layer of the bilayer itself being a “hole injection layer.” In this second case, to avoid confusion, the transport layer is referred to simply as a “hole transport layer” or “HTL” and the art-known “hole injection layer” or “HIL” retains its usual name.
- the devices of the present invention employ relatively nonpolar solvent-soluble semiconducting polymers blended with organometallic emitters as their emissive layers and polar solvent (for example water and/or lower alkanol)-soluble polymers and small molecules as both HIL/HTL and EIL/ETL layers.
- the devices of the present invention can employ two or three luminescent emitters (represented in the Examples as Type I and Type II devices), in a single emissive region, rather than red, green and blue emission in different regions that appear white when averaged by the observer. More than three emitters can be used as well.
- the luminescent emitters can emit white light via fluorescence (from singlet states) or a combination of fluorescence (from singlet states) and phosphorescence (from triplet states).
- White light can be achieved from two or three luminescent emitters blended into a single material that forms a single emissive thin film layer through the combined emission from the host polymer (such as a conjugated polymer) and from the additional emitters such as green and red-emitting components blended into the host polymer.
- a single emissive layer comprising two or three or more emissive centers allows the fabrication of emitting PLEDs and especially white light-emitting PLEDs by solution processing.
- the HIL/HTL and/or EIL/ETL layers provide a means to balance the electron and hole currents and increase the efficiency of the devices.
- using polar solvent-soluble materials as both the HTL and ETL and less polar solvent-soluble materials as the emissive layer allows the fabrication of multilayer PLEDs that emit light with different colors within the visible spectrum, from blue to red and especially white by processing the various layers from solution.
- the strategy of the present invention enables the relatively simple fabrication of bright and efficient multilayer PLEDs, including white-emitting PLEDs that are characterized by a high color rendering index, suitable color temperature and desired CIE coordinates.
- the color rendering index, color temperature and CIE coordinates from these multilayer electrophosphorescent PLEDs are insensitive to brightness, insensitive to the applied voltage and insensitive to the current density.
- the method for fabrication of multilayer PLEDs presented in this invention can be used for development of large-area displays comprising multilayer light-emitting diodes and other large-area multilayer opto-electronic devices processed from solution by printing technology.
- One object of the present invention is to provide a method to produce multilayer PLEDs and especially white light-emitting PLEDs that exhibit high luminous efficiency, high external quantum efficiency and brightness adequate for applications in solid state lighting and as backlights for liquid crystal displays (LCDs).
- LCDs liquid crystal displays
- Another object of the present invention is to produce high-performance multilayer PLEDs by using polar solvent-soluble polymers and small molecules as a hole injection/transporting layer and/or as an electron injection/transporting layer.
- a third object of the present invention is to provide a technology which can be used for development of multilayer displays comprising light-emitting diodes and other multilayer opto-electronic devices processed from solution by printing technology.
- Yet another object of the present invention is to produce multilayer white PLEDs that exhibit white light with high color rendering index, suitable color temperature and desired CIE coordinates.
- a further object of the present invention is to utilize polar solvent-soluble polymers and small molecules as hole injection/transport layers and/or as electron injection/transport layers in PLEDs.
- An additional object of the present invention is to produce multilayer white emitting PLEDs with stable color rendering index, stable color temperature and stable CIE coordinate all of which are insensitive to brightness, applied voltage and current density.
- Yet another object of the present invention is to produce multilayer white light-emitting PLEDs that produce white emissions having CIE x, y-chromaticity coordinates close to the CIE coordinates of pure white light (0.333, 0.333).
- An additional object of the present invention is to produce multilayer white light-emitting PLEDs that produce white emissions having color temperature close to the 6400° K. value characteristic of average daylight or close to the 4500° K. value characteristic of sunlight at solar altitude 20°.
- a further object of the present invention is to produce multilayer white light-emitting PLEDs that produce white emission having color rendering indices in excess of 80.
- Yet another object of the present invention is to produce multilayer white light-emitting PLEDs that produce white emission having color rendering indices in excess of 90.
- FIG. 1 shows the molecular structures of representative materials employed in the fabrication of devices of this invention including: poly(9,9-dioctylfluorene) (FFO); poly(9,9-dioctylfluorene) end-capped with 5-biphenyl-1,3,4-oxadiazole (PFO-ETM) (the electron-transport-moiety); poly(9,9-dioctylfluorene-co-fluorenone) with 1% fluorenone (PFO-F(1%)); tris (2,5-bis-2′-(9′,9′-dihexylfluorene) pyridine) iridium (III), Ir(HFP) 3 ; poly(vinylcarbazole) sulfonic lithium (PVK-S0 3 Li); and 4-(5-(4-tert-butylphenyl)-1,3,4-oxadiazole-2-yl)-biphenyl
- FIG. 2 shows several representative device configurations in schematic cross-section
- FIG. 3 shows the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of PFO-ETM, PVK-S03Li, t-Bu-PBD-S03Na and the work functions of PEDOT:PSS and Ba;
- FIG. 4 shows the HOMO and LUMO energy levels of PFO-ETM, PFO-F (1%) and Ir (HFP) 3 ;
- FIG. 6 shows the electroluminescent spectra obtained from Type I electrophosphorescent PLEDs at different applied voltages
- FIG. 7 shows the electroluminescent spectra obtained from Type II electrophosphorescent PLEDs at different applied voltages
- FIG. 8 shows the CIE (193 1) chromaticity diagram, with coordinates corresponding to the emission from Type I devices ( ⁇ ) and Type II devices ( ⁇ ) biased at different applied voltages. Also shown are the equi-energy point (E) for pure white light (0.333, 0.333) ( ⁇ ) and the coordinates corresponding to color temperatures of 4000° K.( ⁇ ), 5000° K.( ⁇ ) and 6500° K.( ⁇ ). The dotted line indicates different color temperatures; the dotted oval indicates the approximate area where the human eye perceives the color as white;
- FIG. 9 shows the luminance versus applied voltage and current density versus applied voltage for Type I devices
- FIG. 10 shows the luminance versus applied voltage and current density versus applied voltage for Type II devices
- FIG. 11 shows the forward viewing external luminous efficiency (LE ext ) versus current density, J (mA/cm 2 ) for devices with poly(3,4-ethylenedioxythophene):styrene sulfonic acid PEDOT:PSS as the HIL/HTL and t-Bu-PBD-SO 3 Na as the ETL, and for devices with PVK-SO 3 Li as the HTL and t-Bu-PBD-SO 3 Na as the ETL, respectively; and the forward viewing external power efficiency (PE ext , 1 m/W) versus J (mA/cm 2 ) for Type I devices;
- FIG. 12 shows the forward viewing external luminous efficiency (LE ext ) versus current density, J (mA/cm 2 ) for the devices with PEDOT:PSS as the HIL/HTL and t-Bu-PBD-SO 3 Na as the EIL/ETL, and for devices with PVK-SO 3 Li as the HIL/HTL and t-Bu-PBD-SO 3 Na as the EIL/ETL, respectively; and the forward viewing external power efficiency (PE ext , 1 m/W) versus J (mA/cm 2 ) for Type II devices;
- FIG. 13 shows the total external luminous efficiency (LE total ) and the total external power efficiency (PE total , 1 m/W) versus current density, J (mA/cm 2 ) for Type I devices with PEDOT:PSS as the HIL, PVK-SO 3 as the HTL and t-Bu-PBD-SO 3 Na as the EIL/ETL; and
- FIG. 14 shows the total external luminous efficiency (LE total ) and the total external power efficiency (PE total , 1 m/W) versus current density, J (mA/cm 2 ) for Type II devices with PEDOT:PSS as the HIL and PVK-SO 3 Li as the HTL and t-Bu-PBD-SO 3 Na as the EIL/ETL.
- MBL-PPV poly[5-methoxy-2-(4-sulfobutoxy)-1,4-phenylenevinylene
- PFO-ETM poly(9,9-dioctylfluorene) endcapped with electro-transport-moiety for example, poly(9,9-dioctylfluorene) endcapped with 5-biphenyl-1,3,4 oxadiazole
- PVK-SO 3 Li poly(vinylcarbazole) sulfonic lithium
- PEDOT SSS poly(3,4-ethylenedioxythophene): styrene sulfonic acid
- Solvent polarity is defined herein in accord with the teachings of Christian Reichart, Solvents and Solvent Effects in Organic Chemistry, VCH Publishers 2nd ed., 1988. Reichart provides values for relative polarity ranging from a high of 1.000 for water to a low of 0.006 for cyclohexane. Using these relative polarity values, a “polar solvent” is defined to be a solvent having a relative polarity of from 0.400 to 1.000. Such solvents include, for example, water, glycerin, ethylene glycol, methanol, diethylene glycol, ethanol; the propanols, acetonitrile, dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) and mixtures thereof. Water, lower alkanols (C1-C3) and mixtures thereof are preferred polar solvents.
- nonpolar solvent is defined to be a solvent having a relative polarity of from 0.006 to about 0.300.
- solvents include, for example, cyclohexane, pentane, hexane, heptane; carbon tetrachloride, xylene toluene, benzene, diethyl ether, methyl-tert-butyl-ether (MTBE), dioxane, tetrahydrofuran (THF), ethyl acetate, glyme, diglyme and chloroform.
- C6-C8 hydrocarbons and especially benzene and toluene are preferred nonpolar solvents.
- various materials are said to be “differentially soluble” in a “polar” solvent or a “nonpolar” solvent. This means, at its most general, that the material is more soluble in one family of solvents than the other.
- “differential solubility” implies in that a material is at least 150% and more preferably at least 200% and most preferably at least 300% as soluble in one family as in the other.
- PLEDs of the prior art have been made up of a semiconducting luminescent emitter layer 115 contacted with a low work function electron injection electrode 113 and a high work function hole injection electrode 118 .
- PLEDs are supported on a substrate 119 which provides mechanical strength and commonly contain a passivation layer 112 to mechanically and chemically protect the electrode on the side away from the support.
- the positions of support 119 and passivation layer 112 , relative to the hole injection electrode 118 and electron injection electrode 113 are most commonly as depicted in FIG. 2 .
- references to these “support 119 ” and “protective outer layer 112 ” layers may be omitted for simplicity.
- the prior art further contemplated PLEDs which included a bilayer anode made up of an organic hole injection layer 117 located between the hole injection electrode 118 and the emissive layer 115 .
- This bilayer anode hole injection configuration is known [D. Braun and A. Heeger, Appln. Phys. Lett., 119, 58, 1982].
- FIG. 2 depicts three configurations for devices of this invention in which one or two additional “transport” layers 114 and 116 are present.
- two “transport” layers are present they are on opposite sides of the emissive layer 115 (see 10 ).
- one “transport” layer can be on the electron injection side of layer 115 as EIL/ETL 114 (see 11 ) or on the hole injection side of layer 115 as HTL 116 (see 12 ).
- EIL/ETL electron injection side of layer 115
- HTL 116 see 12
- the bilayer anode hole injection electrode of prior art B in FIG. 2 includes an organic hole injection layer 117 .
- hole injection layer is combined with the hole transport layer as a single HIL/HTL organic layer 120 .
- the emissive layer 115 shown in FIG. 2 comprises a blend (mixture) of one or more emitting polymers (or copolymers) with one or more organometallic emitters.
- Preferred emitting polymers are generally conjugated.
- Preferred examples include devices made from PFO or poly(9,9-dioctylfluorene) end-capped with 5-biphenyl-1,3,4-oxadiazol (PFO-ETM) blended with tris (2,5-bis-2′-(9′,9′-dihexylfluorene)pyridine) iridium (III), (Ir(HFP) 3 ) and devices made from blends of PFO-ETM with poly(9,9-dioctylfluorene-co-fluorenone) with 1% fluorenone (PFO-F(1%)) and Ir(HFP) 3 .
- FIG. 1 shows the molecular structures of PFO-ETM, PFO-F(1%) and Ir(HFP) 3 .
- the synthesis of PFO-ETM has been reported in the scientific literature (X. Gong, W. L. Ma, J. C. Ostrowski, K. Bechgaad, G. C. Bazan, D. Moses, A. J. Heeger, S. Xiao, Adv. Func. Mater., 2004, 14,393].
- Other emitting polymers and especially blue-emitting polymers can also be used in the practice of the invention.
- the synthesis of Ir(HFP) 3 has been reported in the scientific literature [J. C. Ostrowski, M. R. Robinson, A. J. Heeger and G. C.
- Ir(HFP) 3 is representative of the useful organometallic emitters which are complexes and compounds having Ir, Pr, Os, Ru or Au or the like as a center atom.
- the polymer materials used in these emissive layers commonly show differential solubility in nonpolar solvents, such as hydrocarbon solvents.
- the materials described herein as preferred are preferred in settings where white light emission is desired.
- the polymers such as PFO-ETM themselves are blue-emitting materials.
- the organometallic emitter and the other host polymers can produce emissions which result in a white overall emission.
- the Electron Injection/Transport Layer ( 114 )
- the electron injection/transport layer (EIL/ETL), typically 20 to 30 nm thick, is cast from solution onto the top surface of emissive layer 115 as shown in FIG. 2 .
- the electron injection/transport layer is fabricated from a semiconducting organic polymer material with a relatively large electron affinity; i.e. with a lowest unoccupied molecular orbital (LUMO) close in energy to that of the bottom of the ⁇ *-band of the luminescent polymer in the emissive layer, for example within about 1 eV.
- the EIL/ETL is fabricated from a material having a LUMO closer to the LUMO of the emissive layer than the work function of the low work function electron injection electrode.
- Examples include t-Bu-PBD SO 3 Na [T. J. Boyd, R. R. Schrock, Macromolecules, 1999, 32, 6608].
- This layer is cast from a polar solvent-based solution such as an aqueous and/or lower alkanol solution.
- the hole transport layer (HTL), typically 20 to 30 nm thick, is cast from solution onto the top surface of hole injection layer 117 . If the hole injection electrode is a single layer anode 118 which does not have a layer 117 , then the layer 116 will be deposited directly in electrode 118 as an HIL/HTL as will explained in paragraph 0054.
- the hole injection/transport layer is fabricated from a semiconducting organic polymer material with a relatively small ionization potential; i.e., with highest occupied molecular orbital (HOMO) close in energy to that of the top of the n-band of the luminescent polymer in the emissive layer, for example within about 1 eV.
- HOMO highest occupied molecular orbital
- the HTL is fabricated from a material having a HOMO closer to the HOMO of the emissive layer than the work function of the hole injection electrode.
- a material having a HOMO closer to the HOMO of the emissive layer than the work function of the hole injection electrode examples include PVK-S03Li [S. Wang, Z. Zeng, S. Yang, L.-T. Weng, P. C. L. Wong, K. Ho, Macromolecules, 2000, 33, 3232.
- This layer is cast from a polar solvent-based solution such as an aqueous and/or lower alkanol solution.
- the devices of the invention may include a bilayer anode.
- One layer of a bilayer anode is generally referred to as a “Hole Injection Layer” or “HIL.” If such a layer is present, then this layer 116 will be referred to as a “Hole Transport Layer” or “HTL.” If a separate Hole Injection Layer is not present then layer 116 can serve both functions and can be referred to as a “Hole Injection Transport Layer” or “HIL/HTL.”
- the Optional Hole Injection Layer ( 117 )
- a hole injection layer 117 When a hole injection layer 117 is present to provide a bilayer anode, it is typically 20 to 30 nm thick and is cast from solution onto the electrode 118 .
- materials used in layer 117 include semiconducting organic polymers such as PEDOT:PSS cast from a polar (aqueous) solution or the precursor of poly(BTPD-Si-PFCB) [S. Liu, X. Z. Jiang, H. Ma, M. S. Liu, A. K.-Y. Jen, Macro., 2000, 33, 3514; X. Gong, D. Moses, A. J. Heeger, S. Liu and A. K.-Y. Jen, Appl. Phys. Lett., 2003, 83, 183].
- PEDOT:PSS is preferred.
- poly(BTPD-Si-PFCB) as hole injection layer, many processing issues existing in PLEDs, brought about by the use of PEDOT:PSS, such as the undesirable etching of emissive polymers, undesirable etching of ITO electrodes, and the formation of micro-shorts can be avoided [G. Greczynski, Th. Kugler and W. R. Salaneck, Thin Solid Films, 1999, 354, 129; M. P. de Jong, L. J. van Ijzendoorn, M. J. A. de Voigt, Appl. Phys. Lett. 2000, 77, 2255].
- the High Work Function Electrode ( 118 )
- the high work function hole injection electrode is typically a transparent conductive metal-metal oxide or sulfide material such as indium-tin oxide (ITO) with resistivity of 20 ohm/square or less and transmission of 89% or greater @ 550 nm. Other materials are available such as thin, transparent layers of gold or silver.
- a “high work function” in this context is generally considered to be a work function of about 4.5 eV or greater.
- This electrode is commonly deposited on the solid support 112 by thermal vapor deposition, electron beam evaporation, RF or Magnetron sputtering, chemical deposition or the like. These same processes can be used to deposit the low work-function electrode 113 as well.
- the principal requirement of the high work function electrode is the combination of a suitable work function, low resistivity and high transparency.
- the Low Work Function Electrode ( 113 )
- the low work function electrode 113 serves as an electron injection contact. It is typically made of a low work function metal or alloy placed on the opposite side of the active emissive polymeric layer 115 from electrode 118 .
- Low work function metals in the context of the present invention include materials with a work function of about 4.3 eV or less and are known in the art to include, for example Ba, Ca, Mg, In and Th. They are often accompanied by a layer of stable metal such as Ag, Au, Al or the like. This serves as a protection layer on top of reactive materials such as Ba, Ca, Tb.
- Other low work function (low ionization potential) conducting materials can be used in place of a conventional metal as the electron injection contact.
- the thickness of the electron injection electrode film is not critical and can be adjusted to achieve the desired surface resistance (surface resistance or sheet resistance is defined as the resistivity divided by the thickness) and can typically vary in the range of from significantly less than 100 ⁇ to about 2000 ⁇ or more. These materials are generally laid down as thin films with the techniques set out in the description of electrode 118 .
- the various active layers 113 - 118 and passivation layer 112 are usually supported by a solid substrate 119 .
- This can be a rigid material such as plastic, glass, silicon, ceramic or the like or a flexible material such as a flexible plastic as well.
- This support may be transparent (as is the support shown in FIG. 2 ) in which case the light can be emitted through it and through the transparent electrode 118 .
- the support can be non-transparent, in which case the transparent electrode 118 , through which light is emitted, is on the surface of the emissive layer away from the support.
- the passivation (protection) layer on the cathode is commonly made up of a stable metal that is typically thermally deposited in vacuum onto the top surface of the low work function metal cathode.
- Useful metals for the passivation layer are known in the art and include, for example, Ag and Al and the like.
- the thickness of the passivation layer is not critical and can be adjusted to achieve the desired surface resistance (surface resistance or sheet resistance is defined as the resistivity divided by the thickness) and can vary in the range of from few hundred Angstroms to more than one thousand Angstroms.
- the PLEDs of this invention may be fabricated using techniques known in the art, such as solution casting, screen printing, contact printing, precursor polymer processing, melt-processing, and the like to lay down the emissive polymer blend layer 115 , hole injection layer 117 and the one or two transport layers 114 and 116 .
- Sputtering, evaporation and the like may be used to lay down the electrode materials in layers 113 and 118 and the passivation materials in layer 112 .
- the present invention provides a method for obtaining efficient electrophosphorescent PLEDs by solution processing.
- the PLED is built up with successive layers as described above.
- the first of the organic layers, hole injection layer 117 of the bilayer electrode is deposited on a transparent metal/metal oxide electrode 118 itself present on the substrate 119 .
- Layer 117 is cast or printed onto the electrode as a solution.
- the solvent is removed by evaporation and the next layer in the sequence, hole transport layer 116 , is cast onto the previously-deposited layer 117 , again as a solution and again with the solvent being removed by evaporation.
- the emissive layer 115 is cast from solution.
- This solution contains the luminescent polymers and the organometallic emitters that make up the emissive layer. Solvent is removed and the next layer, electron transport layer 114 is deposited as a solution which is dried and overcoated by vacuum depositing electron injection electrode 113 followed by passivation layer 112 .
- the layers which bound the emissive layers are differentially soluble in a more polar solvent such as water or a relatively polar organic liquid such as a 1 to 3 carbon alkanol, that is methanol, ethanol, propanol or isopropanol or a blend of water and such alkanol and if the solution of luminescent polymers blended with organometallic emitters from which layer 115 is formed is formed in a suitable relatively nonpolar solvent such as a relatively nonpolar organic solvent, especially a relatively nonpolar hydrocarbon or the like. This prevents these successive layers from disrupting, etching and dissolving one another.
- a more polar solvent such as water or a relatively polar organic liquid such as a 1 to 3 carbon alkanol, that is methanol, ethanol, propanol or isopropanol or a blend of water and such alkanol
- a suitable relatively nonpolar solvent such as a relatively nonpolar organic solvent, especially a relatively nonpolar hydrocarbon or the like.
- the emitted light can be tuned by varying the concentrations.
- efficient white light with stable CIE coordinates, high CRI values and stable color temperature can be achieved from electrophosphorescent PLEDs.
- This invention provides white electrophosphorescent PLEDs which have high brightness, stable CIE coordinates close to CIE coordinates (0.333, 0.333) of pure white light, high CRI values and stable color temperature. And more importantly, the white electrophosphorescent PLEDs described herein have CIE coordinates, CIU values and color temperatures that are insensitive to brightness, applied voltages and applied current density.
- the mechanism for achieving white light from the Type I PLEDs of this invention can be described with reference to the representative emissive layer made up of an Ir(HFP) 3 : PFO-ETM blend.
- the mechanism involves hole trapping on the Ir(HFP) 3 followed by electron trapping on the Ir(HFP) 3 + cation [X. Gong, J.C. Ostrowski, D. Moses, G. C. Bazan, and A. J. Heeger, Appl. Phys. Lett., 2002, 81, 3711].
- a portion of the injected holes (from ITO/PEDOT:PSS or poly(BTPD-Si-PFCB) and electrons (from the Ca/Ag or Ba/Al) recombine on the PFO-ETM main chain to produce blue and/or green light, [X. Gong, P. Iyer, D. Moses, G. C. Bazan, A. J. Heeger, Adv. Func. Mater., 2003, 13, 325].
- Another portion of injected holes and electrons are trapped by Ir(HFP) 3 with subsequent emission of red light from the triplet of Ir(HFP) 3 [X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, A. J.
- Type II PLEDs such as those made from the blends of Ir(HFP) 3 :PFO-F(1%):PFO-ETM, injected holes and electrons recombine by two processes; direct recombination on the main chain (PFO-ETM) to produce blue and/or green emission in parallel with electron and hole trapping on the fluorenone units and on the Ir(HFP) 3 followed by radiative recombination, with green light from PFO-F (1%) [X. Gong, D. Moses and A. J. Heeger, Synthe. Met., 2004, 141, 171 and red light from the triplet excited state of Ir(HFP) 3 [X. Gong, J. C. Ostrowski, D. Moses, G.
- FIG. 3 presents the energy levels of the top of the ⁇ -band (highest occupied molecular orbital, HOMO) and the bottom of the ⁇ *-band (lowest unoccupied molecular orbital, LUMO) of poly(9,9-dioctylfluorene) end-capped with 5-biphenyl-1,3,4-oxadiazol(PFO-ETM), poly(vinylcarbazole) sulfonic lithium (PVK-SO 3 Li) and 4-(5-(4-tert-butylphenyl)-1,3,4-oxadiazole-2-yl)-biphenyl-4′-yl sulfonic sodium (t-Bu-PBD-SO 3 Na) and the work functions of barium (Ba) and poly(3,4-ethylene dioxythiophene): poly(styrene s), poly(styrene s), poly(styrene s), poly(styrene s,
- FIG. 4 shows the corresponding energy levels of PFO-ETM, tris (2,5-bis-2′-(9′,9′-dihexylfluorene) pyridine) iridium (111), Ir(HFP)3, and fluorenone.
- the HOMO energy level of PVK-SO 3 Li is well aligned with the HOMO energy level of PFO-ETM, at ⁇ 5.80 eV, implying a nearly ohmic contact for hole injection from PVK-So 3 Li to PFO-ETM.
- the LUMO of t-Bu-PBD-SO 3 Na, at ⁇ 2.60 eV, is ⁇ 0.10 eV higher than the work function of barium, at ⁇ 2.70 eV.
- this small electron injection barrier will be reduced by the formation of an interface dipole layer at the Ba/t-Bu-PBD-SO 3 Na interface [X. Gong, P. Iyer, D. Moses, G. C. Bazan, A. J.
- the HTL and ETL block the transport of the electrons and holes, respectively, at the interface between the semiconducting emissive polymer layer and the HTL and/or ETL, thereby enhancing the probability of radiative recombination within the emissive layer.
- higher values of luminous efficiency, power efficiency and luminance are achieved (see FIGS. 11 and 12 ).
- the fraction of light emitted in the forward direction is 1/(2n2) of the total where n is the index of refraction of emitter layer [N. C. Greenham, R. H. Friend, and D. D. C. Bradley, Adv. Mater., 1994, 6, 491]. More detailed optical modeling predicted (3 ⁇ 4n 2 ) as the fraction emitted in the forward direction [J. S. Kim, P. H. Ho, N. C. Greenham, and R. H. Friend, J. Appl. Phys., 2000, 88, 1073].
- Forrest and colleagues have obtained similar results; in the small device approximation, they found that the total LE is larger by a factor of 1.7 ⁇ -2.4 than observed in the forward viewing direction [B. W. D'Andrade, S. R. Forrest, Adv. Mater., 2004, 16, 1585; B. W. D'Andrade, R. J. Holmes, and S. R. Forrest, Adv. Mater., 2004, 16,624].
- t-Bu-PBD-SO 3 H was synthesized by a procedure described in the literature [T. J. Boyd, R. R. Schrock, Macromolecules, 1999, 32, 6608]. A concentrated solution of t-Bu-PBD-SO 3 H in water/THF(v/v 6:1) was added into a salt brine to afford a white precipitate. The precipitate was extracted into ethanol and the ethanol was removed to obtain the desired sodium salt t-Bu-PBD-SO 3 Na.
- PFO-ETM, PFO-F (1%) and Ir(HFP) 3 were prepared by dissolving 50 mg PFO-ETM, 20 mg PFO-F (1%) and 5 mg Ir(HFP) 3 into 1 ml toluene, respectively.
- the resulting 0.5 wt.-% Ir(HFP) 3 solution was diluted to 0.05 wt.-% Ir(HFP) 3 .
- the mixtures were stirred overnight at 65° C. and then cooled to room temperature.
- Type I solution 2.4 ⁇ l of a solution of 0.05 wt.-% Ir(HFP) 3 in toluene and 400 ⁇ l of a solution of 5 wt.-% PFO-ETM in toluene were added into 197.6 ⁇ l of pure toluene.
- Type II solution 19.2 ⁇ l of a solution of 0.05 wt.-% Ir(HFP) 3 in toluene and 400 ⁇ l of a solution of wet.-% PFO-ETM in toluene were added into 180.8 ⁇ l of pure toluene.
- a PVK-S03Li solution prepared according to Example 5 was spin-cast at 5000 rpm in nitrogen atmosphere onto a preformed hole injection layer of PEDOT:PSS and thereafter baked at about 85° C. in a vacuum oven for 24 hours to yield a hole transport layer 116 on top of a hole injection layer 117 .
- Alternative hole transport layers 116 can be used such as, for example, poly(BTPD-Si-PFCB).
- Type I and Type II solutions prepared according to Example 4 were spin-cast at 2000 rpm in nitrogen atmosphere onto PVK-S0 3 Li layers 116 prepared according to Example 6, and thereafter baked at 65° C. in a nitrogen atmosphere for 20 minutes to yield a variety of emissive layers 115 on hole transport layers 116 .
- t-Bu-PBD-SO 3 Na solution prepared according to Example 5 was spin-cast at 5000 rpm in nitrogen atmosphere onto the emissive layer 115 and thereafter baked at about 95° C. in vacuum oven for 24 hours to yield a representative electron transport layer 114 on emissive layer 115 .
- a Ba electrode 113 (for electron injection) was formed with a thickness of approximate 100 angstroms onto the t-Bu-PBD-S03Na layer 114 and then a protective Al over layer 112 was deposited with a thickness of approximate 2000 angstroms by vapor deposition at 10 ⁇ 6 Torr.
- a protective Al over layer 112 was deposited with a thickness of approximate 2000 angstroms by vapor deposition at 10 ⁇ 6 Torr.
- Ca or other low work function metals (and their alloys) can be used for the electron injection layer 113 .
- the overlayer 112 can be made using any inert metal, for example, silver or gold.
- Examples 6-9 together demonstrate that multilayer PLEDs can be fabricated by solution processing the organic layers.
- the strong green emission from “blue-emitting” PFO-ETM results from fluorenone defects generated during device fabrication/operation [x. Gong, P. Iyer, D. Moses, G. C. Bazan, A. J. Heeger, Adv. Func. Mater., 2003, 13, 325].
- the broad green emission from PFO-F (1%) originates from excitation energy transfer in the copolymer from the PFO-ETM majority component to the fluorenone minority component.
- the red emission with maximum at 600 nm and a shoulder at 620 is the Ir(HFP) 3 triplet emission.
- Ir(HFP) 3 triplet emission [X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, A. J. Heeger, M. S. Liu, A. K-Y. Jen, Adv. Mat. 2003, 15, 45; J. C. Ostrowski, M. R. Robinson, A. J. Heeger and G. C. Bazan, Chem. Commun., 2002, 7, 784].
- FIG. 6 shows the electroluminescent spectra obtained from Type I devices at different applied voltages.
- White light was generated from two components, PFO-ETM and Ir(HFP) 3 ; both blue and green from PFO-ETM [X. Gong, P. Iyer, D. Moses, G. C. Bazan, A. J. Heeger, Adv. Func. Mater., 2003, 13, 325] and red from Ir(HFP) 3 .
- FIG. 7 shows the electroluminescent spectra obtained from Type II devices at different applied voltages.
- PFO-F (1%) was added into the PFO-ETM:Ir(HFP) 3 blends to fine-tune the color distribution. Therefore, white light was generated by Type II devices from three components, PFO-ETM, PFO-F (1%) and Ir(HFP)3; blue and green from PFO-ETM [X. Gong, P. Iyer, D. Moses, G. C. Bazan, A. J. Heeger, Adv. Func. Mater., 2003, 13, 325] and red from Ir(HFP) 3 , green from PFO-F (1%) [X. Gong, D. Moses, and A. J. Heeger, Synthe. Met. 2004, 141, 171 and red from Ir(HFP) 3 .
- FIG. 8 shows the 1931 CIE chromaticity diagram, with coordinates corresponding to the emission from electrophosphorescent PLEDs: data points are shown for both Type I devices (open squares) and Type II devices (open circles) biased at different applied voltages.
- the specific concentrations used in the Type I and Type II devices were chosen for example only; the CIE coordinates can be changed continuously by changing the composition of the blends. In FIG. 8 , the dotted line indicates different color temperatures; the dotted oval indicates the approximate area where the human eye perceives the color as white.
- FIG. 9 shows the luminance (L) versus voltage (V) and current-density (J) versus voltage (V) characteristics for Type I devices. All devices turn on at approximately 6 V, which is ⁇ 1 V higher than the devices without PVK-SO 3 Li, due to the larger film thickness. Type I devices have L max ⁇ 2.4 10 4 cd/m 2 at 25 V.
- FIG. 10 shows the luminance (L) versus voltage (V) and current-density (J) versus voltage (V) characteristics for Type II devices. All devices turn on at approximately 6 V, which is ⁇ 1 V higher than the devices without PVK-SO 3 Li, due to the larger film thickness. Type II devices have L max ⁇ 2.4 ⁇ 10 4 cd/m 2 at 25 V.
- FIG. 11 shows the forward viewing external luminous efficiency (LE ext ) versus current density, J (mA/cm 2 ) for Type I devices with PEDOT:PSS as the HIL/HTL, t-Bu-PBD-S0 3 Na as the ETL, and PVK-S0 3 Li as the HTL and t-Bu-PBD-S0 3 Na as the ETL, respectively; and the forward viewing external power efficiency (PE ext , lm/W) versus J (mA/cm 2 ).
- the LE ext and PE ext at 200 mA/cm 2 are significantly higher than any reported previously for white OLEDs and PLEDs [J. Kido, H, Shionoya, K, Nagai, Appl. Phys. Lett., 1995, 67, 2281; C. Zhang, A. J. Heeger, J. Appl. Phys., 1998, 84, 1579; Z. Shen, P. E. Burrows, V. Bulvi ⁇ , S. R. Forrest, M. E. Thompson, Science, 1997, 276, 2009; Y. Hamada, T. Sano, H. Fujii, Y. Nishio, Jpn. J. Appl. Phys., 1996, 35, L1339; Y.
- the LE ext from white PLEDs with both PVK-SO 3 Na as HTL and t-Bu-PBD-SO 3 Na as ETL are higher than that with only t-Bu-PBD-SO 3 Na as ETL. Therefore, these results demonstrate that white PLEDs comprising HTL and ETL which reduce the energy barriers for hole and electron injection have the highest LE ext and PE ext and, correspondingly, the highest L at a given J.
- FIG. 12 shows the forward viewing external luminous efficiency (LE ext ) versus current density, J (mA/cm 2 ) for Type II devices with PED0T:PSS as the HIL/HTL, t-Bu-PBD-SO 3 Na as the ETL, and PVK-SO 3 Li as the HTL and t-Bu-PBD-SO 3 Na as the ETL, respectively; and the forward viewing external power efficiency (PE ext /lm/W) versus J (mA/cm 2 ).
- the LE ext from white Type II PLEDs with t-Bu-PBD-SO 3 Na as ETL is higher than that without t-Bu-PBD-SO 3 Na.
- the LE ext from white PLEDs with both PVK-SO 3 Na as HTL and t-Bu-PBD-SO 3 Na as ETL are higher than that only with t-Bu-PBD-SO 3 Na as ETL.
- FIG. 13 shows the total external luminous efficiency (LE total ,) and the total external power efficiency (PE total , lm/W) versus current density J (mA/cM 2 ) for Type I devices with PEDOT:PSS as the HIL, PVK-SO 3 Li as the HTL and t-Bu-PBD-SO 3 Na as the EIL/ETL.
- FIG. 14 shows the total external luminous efficiency (LE total ) and the total external power efficiency (PE total , MW) versus current density J (mA/cm 2 ) for Type II devices with PEDOT:PSS as the HIL and PVK-SO 3 Li as the HTL and t-Bu-PBD-SO 3 Na as the EIL/ETL.
Abstract
Description
- This invention is in the field of organic polymer-based light-emitting diodes. More particularly this invention relates to multilayer polymer light-emitting diodes (PLEDs) that, in certain embodiments, emit white light that is useful for solid state lighting applications. This invention also pertains to methods for preparing these diodes.
- Polymer light-emitting diodes (PLEDs) which employ semiconducting polymers as emitting layers have been demonstrated. A wide range of colors of emission can be achieved by varying the materials present in the emitting layers. Blends of emitting polymers alone and together with organometallic emitters can be used to achieve additional color shades of emitted light including white light.
- LEDs that emit white light are of interest and potential importance for use as back lights in active matrix displays (with color filters) and because they can be used for solid state lighting [A. J. Heeger, Solid State Commu., 1998. 107,673 & Rev. Modem Phys., 2001,73, 681; B. W. D'Andrade, S. R. Forrest, Adv. Mater., 2004, 16, 1585; R. H. Friend, R. W. Gymer, A. B. Holmes, J. H. Burroughes, R. N. Marks, C. Taliani, D. D. C. Bradley, D. A. Dos Santos, J. L. Bredas, M. J. Ögdlund, and. W. R. Salaneck, Nature, 1999, 397, 121]. In such applications, the fabrication of large-area devices and the use of low-cost manufacturing technology will be the major issues. The fabrication of PLEDs by processing the active materials from solution (e.g. by use of ink-jet printing or other printing technologies) promises to be less expensive than that of OLEDs (organic light-emitting diodes based on small molecules) where deposition of the active layers requires the use of vacuum technology [B. W. D'Andrade, S. R. Forrest, Adv. Mater., 2004, 16, 1585] Several approaches have been used to generate white light and light of other colors from OLEDs and PLEDs [J. Kido, H, Shionoya, K, Nagai, Appl. Phys. Lett., 1995, 67, 2281-2283; C. Zhang, A. J. Heeger, J. Appl. Phys., 1998, 84, 1579; Z. Shen, P. E. Burrows, V. Bulvić, S. R. Forrest, M. E. Thompson, Science, 1997, 276, 2009; Y. Hamada, T. Sano, H. Fujii, Y. Nishio, Jpn. J. Appl. Phys., 1996, 35, L1339; Y. Z. Wang, R. G. Sun, F. Meghdadi, G. Leising, A. J. Epstein, Appl. Phys. Lett., 1999, 74, 3613; M. Strukelj, R. H. Jordan, A. Dodabalapur, A.; J. Am. Chem. Soc., 1996, 118, 1213; B. W. D'Andrade, R. J. Holmes, and S. R. Forrest, Adv. Mater., 2004, 16, 624]. In the approaches in the articles listed above, the efficiency was modest and the lifetime was limited by that of the blue emitters [J. Kido, H, Shionoya, K, Nagai, Appl. Phys. Lett., 1995, 67, 2281; Y. Hamada, T. Sano, H. Fujii, Y. Nishio, Jpn. J. Appl. Phys., 1996, 35, L1339; Y. Z. Wang, R. G. Sun, F. Meghdadi, G. Leising, A. J. Epstein, Appl. Phys. Lett., 1999, 74, 3613; M. Strukelj, R. H. Jordan, A. Dodabalapur, A.; J. Am. Chem. Soc., 1996, 118, 1213; U. Scherf, E. J. W. List, Adv. Mater. 2002, 14, 477; S. Setayesh, D. Marsitzky, K. Müllen, Macromolecules, 2000, 33, 2016; X. Gong, P. Iyer, D. Moses, G. C. Bazan, A. J. Heeger, Adv. Func. Mater., 2003, 13, 325].
- PLEDs fabricated with semiconducting polymers doped with organometallic emitters offer the additional promise of “plastic” electronics. Representative examples of such devices are described in U.S. application Ser. No. 10/680,084 filed Oct. 3, 2003. The emissive layers of PLEDs can be fabricated by casting polymers and blends from solution, thereby enabling relatively simple and low cost manufacturing processes [G. D. Müller, A. Falcou, N. Reckefuss, M. Roijhn, V. Wiederhim, P. Rudati, H. Frohne, O. Nuyken, H. Becker, K. Meerholz, Nature, 2003, 421, 829].
- The fabrication techniques most favored for producing multilayer PLEDs include the use of sputtering and various vapor deposition methods to lay down inorganic layers such as high work function metal-metal oxide contacts (electrodes) and protective metallic overlayers. Solvent deposition methods such as spin-casting or printing successive layers from solution can be used to lay down organic polymer emissive layers as well as other layers in the devices. When multiple organic layers are present there can be problems with successive layers interacting. The solvent of a later layer can dissolve or disfigure (etch) a prior layer. It is often desirable to have each layer be smooth and coherent, thus this interaction can be destructive.
- Light may be characterized by three quantities: the CIE (Commission Internationale de l'Eclairage) coordinates, the color temperature (CT) and the color rendering index (CRI). “Pure” white light has CIE coordinates of (0.333, 0.333), and is obtained by balancing the emission of the colors employed. For illumination applications, the CT needs to be equivalent to that of a blackbody source between 3000° K. and 7500° K. Average daylight has CT=6500° K., while a fluorescent lamp (warm white) has CT=3000° K. [R. W. G. Hunt, Measuring Color, 2nd Ed. Ellis Horwood, 1991]. The CRI is a numerical measure of how “true” colors look when viewed with the light source. CRI values range from 0 to 100, with 100 representing true color reproduction. Fluorescent lamps have CRI ratings between 60 and 99. Though a CIU value of at least 70 may be acceptable for certain applications, a preferred white light source will have a CRI of about 80 or higher. The demonstration of PLEDs which emit illumination quality white light with high brightness, high efficiency, suitable CT, high CRI and stable CIE coordinates is of importance to the future of solid state lighting.
- We have now discovered an improvement in multilayer PLEDs that enhances their efficiency and facilitates their fabrication.
- We have found that the addition of an electron transport layer and/or a hole transport layer adjacent to the emissive layer of a PLED improves the PLED's performance. We have further found that these additional layers can be incorporated into PLEDs by solvent processing techniques if the materials employed in these additional layers are differentially soluble in solvents which differ in polarity from the solvents used to dissolve and solvent process the emissive layer.
- Thus, this invention can provide multilayer polymer light-emitting diodes (PLEDs) that in certain embodiment emit white light and are useful for solid state lighting applications. More specifically, the present invention can provide multilayer white PLEDs comprising semiconducting polymers blended with organometallic emitters as a relatively nonpolar solvent-soluble emissive layer, and relatively polar solvent-soluble organic materials (polymers or small molecules) as a hole injection/transport layer (HIL/HTL) and/or as an electron injection/transport layer (EIL/ETL); all layers preferably being cast from the corresponding solutions. The white emission of these preferred materials of the present invention can be used for backlights in liquid crystal displays (LCDs) and for solid state lighting applications. The white light is emitted from the polymer blend in a single emissive layer. The strategy developed in this invention enables the fabrication of multilayer white emitting PLEDs by casting the emissive polymer blends, HIL/HTL, and EIL/ETL from the corresponding solutions. This invention also enables the relatively simple fabrication of multilayer PLEDs which emit illumination quality light in all colors from blue to red and including white light. The methodology presented in this invention enables the relatively simple fabrication of multilayer PLEDs which emit illumination quality white light with high brightness, high efficiency, suitable color temperature, high color rendering index, and stable CIE (Commission Internationale de l'Eclairage) coordinates. The method for fabrication of multilayer PLEDs presented in this invention can be used for large-area multilayer displays and other large-area multilayer opto-electronic devices fabricated by casting the various layers from solution.
- The devices of the present invention employ an emissive layer and at least one of a hole injection/transport layer (HIL/HTL) and an electron injection/transport layer (EIL/ETL) adjacent to the emissive layer. The benefits of the transport layers can be observed in devices which employ a single layer hole injection anode, in which case the hole transport layer may at times be referred to as a “hole injection/transport layer” or “HIL/HTL.” and also in devices which employ a bilayer anode with the second layer of the bilayer itself being a “hole injection layer.” In this second case, to avoid confusion, the transport layer is referred to simply as a “hole transport layer” or “HTL” and the art-known “hole injection layer” or “HIL” retains its usual name. The devices of the present invention employ relatively nonpolar solvent-soluble semiconducting polymers blended with organometallic emitters as their emissive layers and polar solvent (for example water and/or lower alkanol)-soluble polymers and small molecules as both HIL/HTL and EIL/ETL layers. The devices of the present invention can employ two or three luminescent emitters (represented in the Examples as Type I and Type II devices), in a single emissive region, rather than red, green and blue emission in different regions that appear white when averaged by the observer. More than three emitters can be used as well. The luminescent emitters can emit white light via fluorescence (from singlet states) or a combination of fluorescence (from singlet states) and phosphorescence (from triplet states). White light can be achieved from two or three luminescent emitters blended into a single material that forms a single emissive thin film layer through the combined emission from the host polymer (such as a conjugated polymer) and from the additional emitters such as green and red-emitting components blended into the host polymer. A single emissive layer comprising two or three or more emissive centers allows the fabrication of emitting PLEDs and especially white light-emitting PLEDs by solution processing.
- The HIL/HTL and/or EIL/ETL layers provide a means to balance the electron and hole currents and increase the efficiency of the devices. Importantly, using polar solvent-soluble materials as both the HTL and ETL and less polar solvent-soluble materials as the emissive layer allows the fabrication of multilayer PLEDs that emit light with different colors within the visible spectrum, from blue to red and especially white by processing the various layers from solution. The strategy of the present invention enables the relatively simple fabrication of bright and efficient multilayer PLEDs, including white-emitting PLEDs that are characterized by a high color rendering index, suitable color temperature and desired CIE coordinates. Moreover, the color rendering index, color temperature and CIE coordinates from these multilayer electrophosphorescent PLEDs are insensitive to brightness, insensitive to the applied voltage and insensitive to the current density. Furthermore, the method for fabrication of multilayer PLEDs presented in this invention can be used for development of large-area displays comprising multilayer light-emitting diodes and other large-area multilayer opto-electronic devices processed from solution by printing technology.
- One object of the present invention is to provide a method to produce multilayer PLEDs and especially white light-emitting PLEDs that exhibit high luminous efficiency, high external quantum efficiency and brightness adequate for applications in solid state lighting and as backlights for liquid crystal displays (LCDs).
- Another object of the present invention is to produce high-performance multilayer PLEDs by using polar solvent-soluble polymers and small molecules as a hole injection/transporting layer and/or as an electron injection/transporting layer.
- A third object of the present invention is to provide a technology which can be used for development of multilayer displays comprising light-emitting diodes and other multilayer opto-electronic devices processed from solution by printing technology.
- Yet another object of the present invention is to produce multilayer white PLEDs that exhibit white light with high color rendering index, suitable color temperature and desired CIE coordinates.
- A further object of the present invention is to utilize polar solvent-soluble polymers and small molecules as hole injection/transport layers and/or as electron injection/transport layers in PLEDs.
- An additional object of the present invention is to produce multilayer white emitting PLEDs with stable color rendering index, stable color temperature and stable CIE coordinate all of which are insensitive to brightness, applied voltage and current density.
- Yet another object of the present invention is to produce multilayer white light-emitting PLEDs that produce white emissions having CIE x, y-chromaticity coordinates close to the CIE coordinates of pure white light (0.333, 0.333).
- An additional object of the present invention is to produce multilayer white light-emitting PLEDs that produce white emissions having color temperature close to the 6400° K. value characteristic of average daylight or close to the 4500° K. value characteristic of sunlight at
solar altitude 20°. - A further object of the present invention is to produce multilayer white light-emitting PLEDs that produce white emission having color rendering indices in excess of 80.
- Yet another object of the present invention is to produce multilayer white light-emitting PLEDs that produce white emission having color rendering indices in excess of 90.
- This invention will be further described with reference being made to the drawings in which:
-
FIG. 1 shows the molecular structures of representative materials employed in the fabrication of devices of this invention including: poly(9,9-dioctylfluorene) (FFO); poly(9,9-dioctylfluorene) end-capped with 5-biphenyl-1,3,4-oxadiazole (PFO-ETM) (the electron-transport-moiety); poly(9,9-dioctylfluorene-co-fluorenone) with 1% fluorenone (PFO-F(1%)); tris (2,5-bis-2′-(9′,9′-dihexylfluorene) pyridine) iridium (III), Ir(HFP)3; poly(vinylcarbazole) sulfonic lithium (PVK-S03Li); and 4-(5-(4-tert-butylphenyl)-1,3,4-oxadiazole-2-yl)-biphenyl-4′-yl sulfonic sodium (t-Bu-PBD-S03Na); -
FIG. 2 shows several representative device configurations in schematic cross-section; -
FIG. 3 shows the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of PFO-ETM, PVK-S03Li, t-Bu-PBD-S03Na and the work functions of PEDOT:PSS and Ba; -
FIG. 4 shows the HOMO and LUMO energy levels of PFO-ETM, PFO-F (1%) and Ir (HFP)3; -
FIG. 5 shows the electroluminescent spectra of the devices made with pure PFO-ETM, PFO-F (1%) and Ir(HFP)3 doped into PFO-ETM (Ir(HFP)3:PFO-ETM=1 wt.-%), as emissive layers; -
FIG. 6 shows the electroluminescent spectra obtained from Type I electrophosphorescent PLEDs at different applied voltages; -
FIG. 7 shows the electroluminescent spectra obtained from Type II electrophosphorescent PLEDs at different applied voltages; -
FIG. 8 shows the CIE (193 1) chromaticity diagram, with coordinates corresponding to the emission from Type I devices (□□□) and Type II devices (∘∘∘) biased at different applied voltages. Also shown are the equi-energy point (E) for pure white light (0.333, 0.333) (▪) and the coordinates corresponding to color temperatures of 4000° K.(▴), 5000° K.(▾) and 6500° K.(●). The dotted line indicates different color temperatures; the dotted oval indicates the approximate area where the human eye perceives the color as white; -
FIG. 9 shows the luminance versus applied voltage and current density versus applied voltage for Type I devices; -
FIG. 10 shows the luminance versus applied voltage and current density versus applied voltage for Type II devices; -
FIG. 11 shows the forward viewing external luminous efficiency (LEext) versus current density, J (mA/cm2) for devices with poly(3,4-ethylenedioxythophene):styrene sulfonic acid PEDOT:PSS as the HIL/HTL and t-Bu-PBD-SO3Na as the ETL, and for devices with PVK-SO3Li as the HTL and t-Bu-PBD-SO3Na as the ETL, respectively; and the forward viewing external power efficiency (PEext, 1 m/W) versus J (mA/cm2) for Type I devices; -
FIG. 12 shows the forward viewing external luminous efficiency (LEext) versus current density, J (mA/cm2) for the devices with PEDOT:PSS as the HIL/HTL and t-Bu-PBD-SO3Na as the EIL/ETL, and for devices with PVK-SO3Li as the HIL/HTL and t-Bu-PBD-SO3Na as the EIL/ETL, respectively; and the forward viewing external power efficiency (PEext, 1 m/W) versus J (mA/cm2) for Type II devices; -
FIG. 13 shows the total external luminous efficiency (LEtotal) and the total external power efficiency (PEtotal, 1 m/W) versus current density, J (mA/cm2) for Type I devices with PEDOT:PSS as the HIL, PVK-SO3 as the HTL and t-Bu-PBD-SO3Na as the EIL/ETL; and -
FIG. 14 shows the total external luminous efficiency (LEtotal) and the total external power efficiency (PEtotal, 1 m/W) versus current density, J (mA/cm2) for Type II devices with PEDOT:PSS as the HIL and PVK-SO3Li as the HTL and t-Bu-PBD-SO3Na as the EIL/ETL. - Nomenclature and Abbreviations
- In this description of this invention a variety of chemical compounds will be referred to. Some of the compounds being named are depicted in
FIG. 1 . - In addition, the following abbreviations will be employed.
- CIE Commission Internationale de l'Eclairage
- CT color-rendering index
- EIL/ETL electron injection-transport layer
- ETM electron-transport layer
- HIL/HTL hole injection-transport layer
- HIL hole injection layer
- HTL hole transport later
-
HFP 9,9-dihexylfluorene pyridine - HOMO highest occupied molecular orbital
- ITO indium tin oxide
- Ir(HFP)3
tris 2,5-bis-2′(9′,9′ dihexylfluorene) pyridine iridium (III) - LCD liquid crystal display
- LUMO lowest unoccupied molecular orbital
- MEH-PPV poly[2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylenevinylene
- MBL-PPV poly[5-methoxy-2-(4-sulfobutoxy)-1,4-phenylenevinylene
- OLED organic-light-emitting diode
- PLED polymer light emitting diode
- PPV poly(phenylenevinylene)
- PFO poly(9,9-dioctylfluorene)
- PFO-ETM poly(9,9-dioctylfluorene) endcapped with electro-transport-moiety for example, poly(9,9-dioctylfluorene) endcapped with 5-biphenyl-1,3,4 oxadiazole
- PFO-F poly(9,9-dioctyfluorene)-fluorenone
- t-Bu PBD-SO3Na 4-(5-(4-tert-butylphenyl)-1,3,4-oxasiazole-2-yl)biphenyl-4′-yl sulfonic sodium
- PVK poly(vinylcarbazole)
- PVK-SO3Na poly(vinylcarbazole) sulfonic sodium
- PVK-SO3Li poly(vinylcarbazole) sulfonic lithium
- PEDOT: SSS poly(3,4-ethylenedioxythophene): styrene sulfonic acid
- poly(BT[PD-Si-PFCB) poly(bis)tetraphenyldiamino)biphenyl-perfluorocyclobutane
- THF tetrahydrofuran
- DMSO dimethyl sulfoxide
- DMF dimethylformamide
- Definitions
- In this description of this invention and in the claims, at times reference is made to solvents as being “polar” or “nonpolar” and reference is made to a material being “differentially soluble” or having “differential solubility” in “polar” or “nonpolar” solvents.
- Solvent polarity is defined herein in accord with the teachings of Christian Reichart, Solvents and Solvent Effects in Organic Chemistry, VCH Publishers 2nd ed., 1988. Reichart provides values for relative polarity ranging from a high of 1.000 for water to a low of 0.006 for cyclohexane. Using these relative polarity values, a “polar solvent” is defined to be a solvent having a relative polarity of from 0.400 to 1.000. Such solvents include, for example, water, glycerin, ethylene glycol, methanol, diethylene glycol, ethanol; the propanols, acetonitrile, dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) and mixtures thereof. Water, lower alkanols (C1-C3) and mixtures thereof are preferred polar solvents.
- A “nonpolar solvent” is defined to be a solvent having a relative polarity of from 0.006 to about 0.300. Such solvents include, for example, cyclohexane, pentane, hexane, heptane; carbon tetrachloride, xylene toluene, benzene, diethyl ether, methyl-tert-butyl-ether (MTBE), dioxane, tetrahydrofuran (THF), ethyl acetate, glyme, diglyme and chloroform. C6-C8 hydrocarbons and especially benzene and toluene are preferred nonpolar solvents.
- In the processing of this invention various materials are said to be “differentially soluble” in a “polar” solvent or a “nonpolar” solvent. This means, at its most general, that the material is more soluble in one family of solvents than the other. Preferably “differential solubility” implies in that a material is at least 150% and more preferably at least 200% and most preferably at least 300% as soluble in one family as in the other.
- Device Configurations
- As shown as “A” in
FIG. 2 , PLEDs of the prior art have been made up of a semiconductingluminescent emitter layer 115 contacted with a low work functionelectron injection electrode 113 and a high work function hole injection electrode 118. As shown in “A,” PLEDs are supported on asubstrate 119 which provides mechanical strength and commonly contain apassivation layer 112 to mechanically and chemically protect the electrode on the side away from the support. The positions ofsupport 119 andpassivation layer 112, relative to the hole injection electrode 118 andelectron injection electrode 113 are most commonly as depicted inFIG. 2 . One could reverse these positions if desired and put the electron injection electrode on the support without departing from the spirit of the invention. Similarly, in describing the invention and its advantages, at times references to these “support 119” and “protectiveouter layer 112” layers may be omitted for simplicity. - As also shown in
FIG. 2 at “B,” the prior art further contemplated PLEDs which included a bilayer anode made up of an organichole injection layer 117 located between the hole injection electrode 118 and theemissive layer 115. This bilayer anode hole injection configuration is known [D. Braun and A. Heeger, Appln. Phys. Lett., 119, 58, 1982]. -
FIG. 2 , at 10, 11 and 12, depicts three configurations for devices of this invention in which one or two additional “transport” layers 114 and 116 are present. When two “transport” layers are present they are on opposite sides of the emissive layer 115 (see 10). When one “transport” layer is present it can be on the electron injection side oflayer 115 as EIL/ETL 114 (see 11) or on the hole injection side oflayer 115 as HTL 116 (see 12). We have obtained best results when both of EIL/ETL and HTL are present. - It should be kept in mind that the bilayer anode hole injection electrode of prior art B in
FIG. 2 includes an organichole injection layer 117. Inembodiment 13, hole injection layer is combined with the hole transport layer as a single HIL/HTLorganic layer 120. - These individual layers will next be described.
- The Emissive Layer (115)
- The
emissive layer 115 shown inFIG. 2 comprises a blend (mixture) of one or more emitting polymers (or copolymers) with one or more organometallic emitters. Preferred emitting polymers are generally conjugated. Preferred examples include devices made from PFO or poly(9,9-dioctylfluorene) end-capped with 5-biphenyl-1,3,4-oxadiazol (PFO-ETM) blended with tris (2,5-bis-2′-(9′,9′-dihexylfluorene)pyridine) iridium (III), (Ir(HFP)3) and devices made from blends of PFO-ETM with poly(9,9-dioctylfluorene-co-fluorenone) with 1% fluorenone (PFO-F(1%)) and Ir(HFP)3.FIG. 1 shows the molecular structures of PFO-ETM, PFO-F(1%) and Ir(HFP)3. The synthesis of PFO-ETM has been reported in the scientific literature (X. Gong, W. L. Ma, J. C. Ostrowski, K. Bechgaad, G. C. Bazan, D. Moses, A. J. Heeger, S. Xiao, Adv. Func. Mater., 2004, 14,393]. Other emitting polymers and especially blue-emitting polymers can also be used in the practice of the invention. The synthesis of Ir(HFP)3 has been reported in the scientific literature [J. C. Ostrowski, M. R. Robinson, A. J. Heeger and G. C. Bazan, Chem. Commun., 2002, 7, 784]. The synthesis of PFO-F(1%) was also reported [X. Gong, D. Moses and A. J. Heeger, Synth. Met. 2004, 141, 17]. Ir(HFP)3 is representative of the useful organometallic emitters which are complexes and compounds having Ir, Pr, Os, Ru or Au or the like as a center atom. - High-performance PLEDs based on PFO-ETM as host and organometallic emitters as guests have been previously demonstrated. [X. Gong, W. L. Ma, J. C. Ostrowski, K. Bechgaad, G. C. Bazan, D. Moses, A. J. Heeger, S. Xiao, Adv. Func. Mater., 2004, 14, 393; X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, A. J. Heeger, M. S. Liu, A. K-Y. Jen, Adv. Mat. 2003,15,45; X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, A. J. Heeger, J. Poly. Sci. Poly. Phys., 2003, 41, 2691].
- The polymer materials used in these emissive layers commonly show differential solubility in nonpolar solvents, such as hydrocarbon solvents.
- The materials described herein as preferred are preferred in settings where white light emission is desired. The polymers such as PFO-ETM themselves are blue-emitting materials. The organometallic emitter and the other host polymers can produce emissions which result in a white overall emission.
- The Electron Injection/Transport Layer (114)
- The electron injection/transport layer (EIL/ETL), typically 20 to 30 nm thick, is cast from solution onto the top surface of
emissive layer 115 as shown inFIG. 2 . The electron injection/transport layer is fabricated from a semiconducting organic polymer material with a relatively large electron affinity; i.e. with a lowest unoccupied molecular orbital (LUMO) close in energy to that of the bottom of the π*-band of the luminescent polymer in the emissive layer, for example within about 1 eV. Preferably the EIL/ETL is fabricated from a material having a LUMO closer to the LUMO of the emissive layer than the work function of the low work function electron injection electrode. Examples include t-Bu-PBD SO3Na [T. J. Boyd, R. R. Schrock, Macromolecules, 1999, 32, 6608]. This layer is cast from a polar solvent-based solution such as an aqueous and/or lower alkanol solution. - The Hole Transport Layer (116)
- The hole transport layer (HTL), typically 20 to 30 nm thick, is cast from solution onto the top surface of
hole injection layer 117. If the hole injection electrode is a single layer anode 118 which does not have alayer 117, then thelayer 116 will be deposited directly in electrode 118 as an HIL/HTL as will explained in paragraph 0054. The hole injection/transport layer is fabricated from a semiconducting organic polymer material with a relatively small ionization potential; i.e., with highest occupied molecular orbital (HOMO) close in energy to that of the top of the n-band of the luminescent polymer in the emissive layer, for example within about 1 eV. Preferably the HTL is fabricated from a material having a HOMO closer to the HOMO of the emissive layer than the work function of the hole injection electrode. Examples include PVK-S03Li [S. Wang, Z. Zeng, S. Yang, L.-T. Weng, P. C. L. Wong, K. Ho, Macromolecules, 2000, 33, 3232. This layer is cast from a polar solvent-based solution such as an aqueous and/or lower alkanol solution. - The devices of the invention may include a bilayer anode. One layer of a bilayer anode is generally referred to as a “Hole Injection Layer” or “HIL.” If such a layer is present, then this
layer 116 will be referred to as a “Hole Transport Layer” or “HTL.” If a separate Hole Injection Layer is not present then layer 116 can serve both functions and can be referred to as a “Hole Injection Transport Layer” or “HIL/HTL.” - The Optional Hole Injection Layer (117)
- When a
hole injection layer 117 is present to provide a bilayer anode, it is typically 20 to 30 nm thick and is cast from solution onto the electrode 118. Examples of materials used inlayer 117 include semiconducting organic polymers such as PEDOT:PSS cast from a polar (aqueous) solution or the precursor of poly(BTPD-Si-PFCB) [S. Liu, X. Z. Jiang, H. Ma, M. S. Liu, A. K.-Y. Jen, Macro., 2000, 33, 3514; X. Gong, D. Moses, A. J. Heeger, S. Liu and A. K.-Y. Jen, Appl. Phys. Lett., 2003, 83, 183]. PEDOT:PSS is preferred. On the other hand, by using poly(BTPD-Si-PFCB) as hole injection layer, many processing issues existing in PLEDs, brought about by the use of PEDOT:PSS, such as the undesirable etching of emissive polymers, undesirable etching of ITO electrodes, and the formation of micro-shorts can be avoided [G. Greczynski, Th. Kugler and W. R. Salaneck, Thin Solid Films, 1999, 354, 129; M. P. de Jong, L. J. van Ijzendoorn, M. J. A. de Voigt, Appl. Phys. Lett. 2000, 77, 2255]. - It will be noted that the advantages of using an emissive layer made of polymers differentially soluble in nonpolar solvents with transfer layers made of materials differentially soluble in polar solvents also are achieved when the optional hole injection layer is made of materials differentially soluble in polar solvents. This means that in
embodiment 13 ofFIG. 2 where a single hole injection/transport layer 120 is employed, it is advantageously differentially soluble in a polar solvent to achieve the desired processing advantages. The materials in thislayer 120 can essentially duplicate the materials inlayer 117 andlayer 116, if desired. - The High Work Function Electrode (118)
- The high work function hole injection electrode is typically a transparent conductive metal-metal oxide or sulfide material such as indium-tin oxide (ITO) with resistivity of 20 ohm/square or less and transmission of 89% or greater @ 550 nm. Other materials are available such as thin, transparent layers of gold or silver. A “high work function” in this context is generally considered to be a work function of about 4.5 eV or greater. This electrode is commonly deposited on the
solid support 112 by thermal vapor deposition, electron beam evaporation, RF or Magnetron sputtering, chemical deposition or the like. These same processes can be used to deposit the low work-function electrode 113 as well. The principal requirement of the high work function electrode is the combination of a suitable work function, low resistivity and high transparency. - The Low Work Function Electrode (113)
- The low
work function electrode 113 serves as an electron injection contact. It is typically made of a low work function metal or alloy placed on the opposite side of the active emissivepolymeric layer 115 from electrode 118. Low work function metals in the context of the present invention include materials with a work function of about 4.3 eV or less and are known in the art to include, for example Ba, Ca, Mg, In and Th. They are often accompanied by a layer of stable metal such as Ag, Au, Al or the like. This serves as a protection layer on top of reactive materials such as Ba, Ca, Tb. Other low work function (low ionization potential) conducting materials can be used in place of a conventional metal as the electron injection contact. The thickness of the electron injection electrode film is not critical and can be adjusted to achieve the desired surface resistance (surface resistance or sheet resistance is defined as the resistivity divided by the thickness) and can typically vary in the range of from significantly less than 100 Å to about 2000 Å or more. These materials are generally laid down as thin films with the techniques set out in the description of electrode 118. - The Support (119)
- The various active layers 113-118 and
passivation layer 112 are usually supported by asolid substrate 119. This can be a rigid material such as plastic, glass, silicon, ceramic or the like or a flexible material such as a flexible plastic as well. This support may be transparent (as is the support shown inFIG. 2 ) in which case the light can be emitted through it and through the transparent electrode 118. Alternatively, the support can be non-transparent, in which case the transparent electrode 118, through which light is emitted, is on the surface of the emissive layer away from the support. - The Passivation Layer (112)
- The passivation (protection) layer on the cathode is commonly made up of a stable metal that is typically thermally deposited in vacuum onto the top surface of the low work function metal cathode. Useful metals for the passivation layer are known in the art and include, for example, Ag and Al and the like. The thickness of the passivation layer is not critical and can be adjusted to achieve the desired surface resistance (surface resistance or sheet resistance is defined as the resistivity divided by the thickness) and can vary in the range of from few hundred Angstroms to more than one thousand Angstroms.
- Fabrication Methods
- The PLEDs of this invention may be fabricated using techniques known in the art, such as solution casting, screen printing, contact printing, precursor polymer processing, melt-processing, and the like to lay down the emissive
polymer blend layer 115,hole injection layer 117 and the one or twotransport layers 114 and 116. Sputtering, evaporation and the like may be used to lay down the electrode materials inlayers 113 and 118 and the passivation materials inlayer 112. - In a preferred embodiment, the present invention provides a method for obtaining efficient electrophosphorescent PLEDs by solution processing. The PLED is built up with successive layers as described above. In a most typical embodiment the first of the organic layers,
hole injection layer 117 of the bilayer electrode is deposited on a transparent metal/metal oxide electrode 118 itself present on thesubstrate 119.Layer 117 is cast or printed onto the electrode as a solution. The solvent is removed by evaporation and the next layer in the sequence,hole transport layer 116, is cast onto the previously-depositedlayer 117, again as a solution and again with the solvent being removed by evaporation. Next theemissive layer 115 is cast from solution. This solution contains the luminescent polymers and the organometallic emitters that make up the emissive layer. Solvent is removed and the next layer, electron transport layer 114 is deposited as a solution which is dried and overcoated by vacuum depositingelectron injection electrode 113 followed bypassivation layer 112. In this embodiment it is advantageous if the layers which bound the emissive layers are differentially soluble in a more polar solvent such as water or a relatively polar organic liquid such as a 1 to 3 carbon alkanol, that is methanol, ethanol, propanol or isopropanol or a blend of water and such alkanol and if the solution of luminescent polymers blended with organometallic emitters from whichlayer 115 is formed is formed in a suitable relatively nonpolar solvent such as a relatively nonpolar organic solvent, especially a relatively nonpolar hydrocarbon or the like. This prevents these successive layers from disrupting, etching and dissolving one another. - By processing the emissive layer and the one or two transport layers from solutions, and particularly solutions in a less polar solvent for the emissive layer and in more polar solvents for the transport layers, the emitted light can be tuned by varying the concentrations. Thus, by processing from solution, efficient white light with stable CIE coordinates, high CRI values and stable color temperature can be achieved from electrophosphorescent PLEDs.
- This invention provides white electrophosphorescent PLEDs which have high brightness, stable CIE coordinates close to CIE coordinates (0.333, 0.333) of pure white light, high CRI values and stable color temperature. And more importantly, the white electrophosphorescent PLEDs described herein have CIE coordinates, CIU values and color temperatures that are insensitive to brightness, applied voltages and applied current density.
- High brightness, stable CIE coordinates close to those of pure white light (0.333, 0.333) high CRI values, and stable color temperature are critical parameters for light sources that are useful for solid state lighting applications [D. B. Judd and G. Wyszelki, Color in Business, Science and Industry, 3th ed. (John Wiley & Sons) 1975, pp. 91-388; G. Wyszelki and W. S. Stiles, Color Science, 2nd ed. (Wiley, New York) 1982, pp. 117-2321. Thus by processing all active layers from the solutions, high brightness, stable CIE coordinates close to (0.333, 0.333), high CRI values and stable color temperature are obtainable from multilayer white emitting PLEDs. Therefore, this invention discloses a method for obtaining high performance multilayer white PLEDs; a method which is useful for solid state lighting applications.
- Mechanism for Generating White Light
- The mechanism for achieving white light from the Type I PLEDs of this invention can be described with reference to the representative emissive layer made up of an Ir(HFP)3: PFO-ETM blend. In this case the mechanism involves hole trapping on the Ir(HFP)3 followed by electron trapping on the Ir(HFP)3 + cation [X. Gong, J.C. Ostrowski, D. Moses, G. C. Bazan, and A. J. Heeger, Appl. Phys. Lett., 2002, 81, 3711]. In this representative white emitting PLEDs, a portion of the injected holes (from ITO/PEDOT:PSS or poly(BTPD-Si-PFCB) and electrons (from the Ca/Ag or Ba/Al) recombine on the PFO-ETM main chain to produce blue and/or green light, [X. Gong, P. Iyer, D. Moses, G. C. Bazan, A. J. Heeger, Adv. Func. Mater., 2003, 13, 325]. Another portion of injected holes and electrons are trapped by Ir(HFP)3 with subsequent emission of red light from the triplet of Ir(HFP)3 [X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, A. J. Heeger, M. S. Liu, A. K-Y. Jen, Adv. Mat. 2003, 15, 45; X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, A. J. Heeger, J. Poly. Sci. Poly. Phys. 2003, 41, 2691; X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, and A. J. Heeger, Appl. Phys. Lett., 2002, 81,3711].
- In the Type II PLEDs, such as those made from the blends of Ir(HFP)3:PFO-F(1%):PFO-ETM, injected holes and electrons recombine by two processes; direct recombination on the main chain (PFO-ETM) to produce blue and/or green emission in parallel with electron and hole trapping on the fluorenone units and on the Ir(HFP)3 followed by radiative recombination, with green light from PFO-F (1%) [X. Gong, D. Moses and A. J. Heeger, Synthe. Met., 2004, 141, 171 and red light from the triplet excited state of Ir(HFP)3 [X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, A. J. Heeger, M. S. Liu, A. K-Y. Jen, Adv. Mat. 2003, 15, 45; X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, A. J. Heeger, J. Poly. Sci. Poly. Phys. 2003, 41, 2691; X. Gong, J. C. Ostrowski, M. R. Robinson, D. Moses, G. C. Bazan, and A. J. Heeger, Adv. Mat., 2002, 14, 581; X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, and A. J. Heeger, Appl. Phys. Lett., 2002, 81, 3711].
- Approaching Balanced Charge Injection and Transport in White PLEDs
- The performance improvements attained by the addition of the hole transport layer and the electron transport layer can be explained by reference to
FIGS. 3 and 4 .FIG. 3 presents the energy levels of the top of the π-band (highest occupied molecular orbital, HOMO) and the bottom of the π*-band (lowest unoccupied molecular orbital, LUMO) of poly(9,9-dioctylfluorene) end-capped with 5-biphenyl-1,3,4-oxadiazol(PFO-ETM), poly(vinylcarbazole) sulfonic lithium (PVK-SO3Li) and 4-(5-(4-tert-butylphenyl)-1,3,4-oxadiazole-2-yl)-biphenyl-4′-yl sulfonic sodium (t-Bu-PBD-SO3Na) and the work functions of barium (Ba) and poly(3,4-ethylene dioxythiophene): poly(styrene sulfonic acid) (PED0T:PSS).FIG. 4 shows the corresponding energy levels of PFO-ETM, tris (2,5-bis-2′-(9′,9′-dihexylfluorene) pyridine) iridium (111), Ir(HFP)3, and fluorenone. - The HOMO energy level of PVK-SO3Li, at −5.75 eV, is well aligned with the HOMO energy level of PFO-ETM, at −5.80 eV, implying a nearly ohmic contact for hole injection from PVK-So3Li to PFO-ETM. The LUMO of t-Bu-PBD-SO3Na, at −2.60 eV, is −0.10 eV higher than the work function of barium, at −2.70 eV. However, even this small electron injection barrier will be reduced by the formation of an interface dipole layer at the Ba/t-Bu-PBD-SO3Na interface [X. Gong, P. Iyer, D. Moses, G. C. Bazan, A. J. Heeger, Adv. Func. Mater., 2003, 13, 325; A. Rajagopal, C. I. Wu, A. Kahn, J. Appl. Phys., 1998, 83, 2649; S. T. Lee, X. Y. Hou, M. G. Mason, C. W. Tang, Appl. Phys. Lett., 1998, 72, 1593]. Therefore, the use of PVK-SO3Li as the hole injection/transport layer from the anode to the emissive polymer layer and t-Bu-PBD-SO3Na as the electron injection/transport layer from the cathode to the emissive polymer layer results in improved transport and high performance white light-emitting PLEDs (see
FIGS. 9-14 for results demonstrating this). - In addition, the HTL and ETL block the transport of the electrons and holes, respectively, at the interface between the semiconducting emissive polymer layer and the HTL and/or ETL, thereby enhancing the probability of radiative recombination within the emissive layer. As a result, higher values of luminous efficiency, power efficiency and luminance are achieved (see
FIGS. 11 and 12 ). - Solid State Lighting
- For solid state lighting applications, one should include the light emitted through the surface and edge of the glass/ITO substrate when calculating the total efficiency [H. A. E. Keitz, “Light Calculations and Measurements,” 2nd Edition, Macmillan and Co Ltd, 1971; A. D. Ryer, “Light Measurement Handbook.” International Light Inc., 1998]. Assuming typical values for the refractive indices of the glass (n=1.5), IT0 (n=1.8-2.0) and polymer (n=1.6-1.8), the critical angle, θ, between the direction of the light emitted in the polymer layer and the substrate surface normal is ˜36° at the air-polymer interface and ˜62° at the glass-polymer interfaces [B. W. D'Andrade, R. J. Holmes, and S. R. Forrest, Adv. Mater., 2004, 16, 624; M. H. Lu, J. C. Sturm, J. Appl. Phys., 2002, 91, 595; J. Kido, Y. Lizurni, Appl. Phys. Lett., 1998, 73, 2721; N.C. Greenham, R. H. Friend, and D. D. C. Bradley, Adv. Mater., 1994, 6, 491]. Light incident on the interface at an angle greater than the critical angle will be totally internally reflected within the glass/ITO and then waveguided within the device. Although some of the guided light escapes by scattering, the remainder is either partially absorbed within the device or coupled out at the edges of the glass/ITO substrate. Theoretically, the fraction of light emitted in the forward direction is 1/(2n2) of the total where n is the index of refraction of emitter layer [N. C. Greenham, R. H. Friend, and D. D. C. Bradley, Adv. Mater., 1994, 6, 491]. More detailed optical modeling predicted (¾n2) as the fraction emitted in the forward direction [J. S. Kim, P. H. Ho, N. C. Greenham, and R. H. Friend, J. Appl. Phys., 2000, 88, 1073]. Through a series of experiments using an integrating sphere, Cao et al. demonstrated that the measured reduction factor is approximately a factor of 2-2.5 less than the theoretical value, (2n2)≈6 (assuming n=1.7 for emitted layer); i.e. closer to 4n2/3≈3.85 [Y. Cao, I. D. Parker, G. Yu, C. Zhang, and A. J. Heeger, Nature, 1999, 397, 414]. Forrest and colleagues have obtained similar results; in the small device approximation, they found that the total LE is larger by a factor of 1.7˜-2.4 than observed in the forward viewing direction [B. W. D'Andrade, S. R. Forrest, Adv. Mater., 2004, 16, 1585; B. W. D'Andrade, R. J. Holmes, and S. R. Forrest, Adv. Mater., 2004, 16,624].
- Synthesis of PVK-SO3Li: The sulfonation of PVK was performed by a procedure described in the literature [S. Wang, Z. Zeng, S. Yang, L.-T. Weng, P. C. L. Wong, K. Ho, Macromolecules, 2000, 33, 3232]. The degree of sulfonation of PVK was about 28%. The sulfonated PVK was dissolved in a minimum amount of hot ethanol, and the resulting solution was cooled down to room temperature. To this solution was added excess EtOLi solution in ethanol and white precipitate was formed. The precipitate was collected by filtration, washed with cooled ethanol and dried under vacuum to obtain the lithium salt PVK-SO3Li.
- Synthesis of t-Bu-PBD-SO3Na: t-Bu-PBD-SO3H was synthesized by a procedure described in the literature [T. J. Boyd, R. R. Schrock, Macromolecules, 1999, 32, 6608]. A concentrated solution of t-Bu-PBD-SO3H in water/THF(v/v 6:1) was added into a salt brine to afford a white precipitate. The precipitate was extracted into ethanol and the ethanol was removed to obtain the desired sodium salt t-Bu-PBD-SO3Na.
- Three stock solutions, PFO-ETM, PFO-F (1%) and Ir(HFP)3 were prepared by dissolving 50 mg PFO-ETM, 20 mg PFO-F (1%) and 5 mg Ir(HFP)3 into 1 ml toluene, respectively. The resulting 0.5 wt.-% Ir(HFP)3 solution was diluted to 0.05 wt.-% Ir(HFP)3. The mixtures were stirred overnight at 65° C. and then cooled to room temperature.
- This example demonstrates that the emissive materials used in the practice of this invention are soluble in common nonpolar organic solvents.
- Preparation of Type I solution: 2.4 μl of a solution of 0.05 wt.-% Ir(HFP)3 in toluene and 400 μl of a solution of 5 wt.-% PFO-ETM in toluene were added into 197.6 μl of pure toluene.
- Preparation of Type II solution: 19.2 μl of a solution of 0.05 wt.-% Ir(HFP)3 in toluene and 400 μl of a solution of wet.-% PFO-ETM in toluene were added into 180.8 μl of pure toluene.
- This example demonstrates that solutions of the emissive materials can be made in nonpolar organic solvent at desired concentrations by blending conjugated polymers with organometallic emitters.
- A solution of 0.5 wt.-% PVK-S033Li in ethanol was prepared.
- A solution of 0.5 wt.-% t-Bu-PBD-S03Na in ethanol was prepared.
- This example demonstrates that solutions of PVK-S03Li and t-Bu-PBD-SO3Na can be made at desired concentrations in polar solvents.
- A PVK-S03Li solution prepared according to Example 5 was spin-cast at 5000 rpm in nitrogen atmosphere onto a preformed hole injection layer of PEDOT:PSS and thereafter baked at about 85° C. in a vacuum oven for 24 hours to yield a
hole transport layer 116 on top of ahole injection layer 117. Alternativehole transport layers 116 can be used such as, for example, poly(BTPD-Si-PFCB). - Type I and Type II solutions prepared according to Example 4 were spin-cast at 2000 rpm in nitrogen atmosphere onto PVK-S03Li layers 116 prepared according to Example 6, and thereafter baked at 65° C. in a nitrogen atmosphere for 20 minutes to yield a variety of
emissive layers 115 on hole transport layers 116. - t-Bu-PBD-SO3Na solution prepared according to Example 5 was spin-cast at 5000 rpm in nitrogen atmosphere onto the
emissive layer 115 and thereafter baked at about 95° C. in vacuum oven for 24 hours to yield a representative electron transport layer 114 onemissive layer 115. - A Ba electrode 113 (for electron injection) was formed with a thickness of approximate 100 angstroms onto the t-Bu-PBD-S03Na layer 114 and then a protective Al over
layer 112 was deposited with a thickness of approximate 2000 angstroms by vapor deposition at 10−6 Torr. [X. Gong, J. C. Ostrowski, M. R. Robinson, D. Moses, G. C. Bazan, and A. J. Heeger, Adv. Mat. 2002, 14, 581; X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, A. J. Heeger, M. S. Liu, A. K-Y. Jen, Adv. Mat. 2003, 15, 45]. - Ca or other low work function metals (and their alloys) can be used for the
electron injection layer 113. - The
overlayer 112 can be made using any inert metal, for example, silver or gold. - Examples 6-9 together demonstrate that multilayer PLEDs can be fabricated by solution processing the organic layers.
-
FIG. 5 shows the electroluminescent spectra obtained from devices made from pure PFO-ETM, PFO-F (1%) and Ir(HFP)3 doped into PFO-ETM (at a concentration of Ir(HFP)3:/PFO-ETM=1 wt. %). The strong green emission from “blue-emitting” PFO-ETM results from fluorenone defects generated during device fabrication/operation [x. Gong, P. Iyer, D. Moses, G. C. Bazan, A. J. Heeger, Adv. Func. Mater., 2003, 13, 325]. The broad green emission from PFO-F (1%) originates from excitation energy transfer in the copolymer from the PFO-ETM majority component to the fluorenone minority component. [X. Gong, D. Moses and A. J. Heeger, Synthe. Met. 2004, 141, 17]. The red emission with maximum at 600 nm and a shoulder at 620 is the Ir(HFP)3 triplet emission. [X. Gong, J. C. Ostrowski, D. Moses, G. C. Bazan, A. J. Heeger, M. S. Liu, A. K-Y. Jen, Adv. Mat. 2003, 15, 45; J. C. Ostrowski, M. R. Robinson, A. J. Heeger and G. C. Bazan, Chem. Commun., 2002, 7, 784]. -
FIG. 6 shows the electroluminescent spectra obtained from Type I devices at different applied voltages. White light was generated from two components, PFO-ETM and Ir(HFP)3; both blue and green from PFO-ETM [X. Gong, P. Iyer, D. Moses, G. C. Bazan, A. J. Heeger, Adv. Func. Mater., 2003, 13, 325] and red from Ir(HFP)3. -
FIG. 7 shows the electroluminescent spectra obtained from Type II devices at different applied voltages. In this white light PLED, PFO-F (1%) was added into the PFO-ETM:Ir(HFP)3 blends to fine-tune the color distribution. Therefore, white light was generated by Type II devices from three components, PFO-ETM, PFO-F (1%) and Ir(HFP)3; blue and green from PFO-ETM [X. Gong, P. Iyer, D. Moses, G. C. Bazan, A. J. Heeger, Adv. Func. Mater., 2003, 13, 325] and red from Ir(HFP)3, green from PFO-F (1%) [X. Gong, D. Moses, and A. J. Heeger, Synthe. Met. 2004, 141, 171 and red from Ir(HFP)3. - The CIE coordinates, CT and CRI were quantitatively evaluated from the electroluminescence spectra obtained in Example 12 [G. Wyszelki and W. S. Stiles, Color Science, 2nd ed. (Wiley, New York) 1982; D. B. Judd and G. Wyszecki, Color in Business, Science and Industry, 3rd ed. (John Wiley & Sons) 1975].
-
FIG. 8 shows the 1931 CIE chromaticity diagram, with coordinates corresponding to the emission from electrophosphorescent PLEDs: data points are shown for both Type I devices (open squares) and Type II devices (open circles) biased at different applied voltages. For Type I devices, the CIE coordinates shift from (0.328, 0.334) at J=0.10 mA/cm2 to (0.296, 0.290) at J=33 mA/cm2; For Type II devices, the CIE coordinates shift from (0.380, 0.400) at J=0.2 mA/cm2; to (0.346, 0.368) at J=115 mA/cm2. All are very close to the CIE coordinates for pure white light, (0.333, 0.333). The stability of the CIE coordinates as a function of applied voltage is much better than reported previously for white PLEDs/OLEDs [J. Kido, H, Shionoya, K, Nagai, Appl. Phys. Lett., 1995,67,2281; Y. Hamada, T. Sano, H. Fujii, Y. Nishio, Jpn. J. Appl. Phys., 1996, 35, L1339; M. Strukelj, R. H. Jordan, A. Dodabalapur, A.; J. Am. Chem. Soc., 1996,118, 1213; B. W. D'Andrade, R. J. Holmes, and S. R. Forrest, Adv. Mater., 2004, 16, 624; Kido, H. Hongawa, K. Okuyama and K. Nagai, Appl. Phys. Lett. 1994, 64, 815; Y. Z. Wang, R. G. Sun, F. Meghdadi, G. Leising, A. J. Epstein, Appl. Phys. Lett., 1999, 74, 3613]. - Type I devices have CT ˜6400° K. (see
FIG. 8 ), very close to the CT of average daylight (6500° K.), [R. W. G. Hunt, Measuring Color, 2nd Ed. Ellis Horwood, 1991] and CRI=92. Type II devices have CT ˜4500° K. (seeFIG. 4 ), very close to the CT of sunlight atsolar altitude 20° (4700° K.) [R. W. G. Hunt, Measuring Color, 2nd Ed. Ellis Horwood, 1991], and CRI=86 (all values insensitive to J). The specific concentrations used in the Type I and Type II devices were chosen for example only; the CIE coordinates can be changed continuously by changing the composition of the blends. InFIG. 8 , the dotted line indicates different color temperatures; the dotted oval indicates the approximate area where the human eye perceives the color as white. -
FIG. 9 shows the luminance (L) versus voltage (V) and current-density (J) versus voltage (V) characteristics for Type I devices. All devices turn on at approximately 6 V, which is ˜1 V higher than the devices without PVK-SO3Li, due to the larger film thickness. Type I devices have Lmax≈2.4 104 cd/m2 at 25 V. -
FIG. 10 shows the luminance (L) versus voltage (V) and current-density (J) versus voltage (V) characteristics for Type II devices. All devices turn on at approximately 6 V, which is ˜1 V higher than the devices without PVK-SO3Li, due to the larger film thickness. Type II devices have Lmax≈2.4×104 cd/m2 at 25 V. -
FIG. 11 shows the forward viewing external luminous efficiency (LEext) versus current density, J (mA/cm2) for Type I devices with PEDOT:PSS as the HIL/HTL, t-Bu-PBD-S03Na as the ETL, and PVK-S03Li as the HTL and t-Bu-PBD-S03Na as the ETL, respectively; and the forward viewing external power efficiency (PEext, lm/W) versus J (mA/cm2). - For display applications, a Lambertian intensity profile was assumed; the forward viewing efficiencies, LEext and PEext shown in
FIG. 11 , were measured with the following results: [K. Müllen, Editor, Electroluminescence-from Synthesis to Devices, Wiley-VCH, 2005 (in press). Type I devices have LEext=10.4 cd/A, L=2391 cd/m2 and PEext=3 lm/W at J=23 mA/cm2 (V=11 V); Note that even at J=200 mA/cm2, the Type I devices have L=19500 cd/m2, LEext=9.5 cd/A and PEext=2 lm/W. The LEext and PEext at 200 mA/cm2 are significantly higher than any reported previously for white OLEDs and PLEDs [J. Kido, H, Shionoya, K, Nagai, Appl. Phys. Lett., 1995, 67, 2281; C. Zhang, A. J. Heeger, J. Appl. Phys., 1998, 84, 1579; Z. Shen, P. E. Burrows, V. Bulvić, S. R. Forrest, M. E. Thompson, Science, 1997, 276, 2009; Y. Hamada, T. Sano, H. Fujii, Y. Nishio, Jpn. J. Appl. Phys., 1996, 35, L1339; Y. Z. Wang, R. G. Sun, F. Meghdadi, G. Leising, A. J. Epstein, Appl. Phys. Lett., 1999, 74, 3613; M. Strukelj, R. H. Jordan, A. Dodabalapur, A.; J. Am. Chem. Soc., 1996, 118, 1213; B. W. D'Andrade, R. J. Holmes, and S. R. Forrest, Adv. Mater., 2004, 16, 6241. - As shown in
FIG. 11 , the LEext from white PLEDs with t-Bu-PBD-SO3Na as is higher than that without t-Bu-PBD-SO3Na. Similarly, the LEext from white PLEDs with both PVK-SO3Na as HTL and t-Bu-PBD-SO3Na as ETL are higher than that with only t-Bu-PBD-SO3Na as ETL. Therefore, these results demonstrate that white PLEDs comprising HTL and ETL which reduce the energy barriers for hole and electron injection have the highest LEext and PEext and, correspondingly, the highest L at a given J. -
FIG. 12 shows the forward viewing external luminous efficiency (LEext) versus current density, J (mA/cm2) for Type II devices with PED0T:PSS as the HIL/HTL, t-Bu-PBD-SO3Na as the ETL, and PVK-SO3Li as the HTL and t-Bu-PBD-SO3Na as the ETL, respectively; and the forward viewing external power efficiency (PEext/lm/W) versus J (mA/cm2). - The measurement approach of Example 18 was repeated LEext=7.2 cd/A, L=882 cd/m2 and PEext=1.5 lm/W at J=12 mA/cm2 (V=15 V). Note that even at J=200 mA/cm2, Type II devices have L=9600 cd/m2, LEext=4.8 cd/A and PEext=0.65 lm/W. Again, the LEext and PEext at 200 mA/cm2 are significantly higher than any reported previously for white OLEDs and PLEDs.
- Moreover, as shown in
FIG. 12 , the LEext from white Type II PLEDs with t-Bu-PBD-SO3Na as ETL is higher than that without t-Bu-PBD-SO3Na. Similarly, the LEext from white PLEDs with both PVK-SO3Na as HTL and t-Bu-PBD-SO3Na as ETL are higher than that only with t-Bu-PBD-SO3Na as ETL. - For solid state lighting applications, a Lambertian intensity profile was assumed; the total external luminous efficiency (LEtotal) and power efficiency (PEtotal) were measured with the results shown in
FIGS. 13 and 14 : [N/. C. Greenham, R. H. Friend, and D. D. C. Bradley, Adv. Mater., 1994, 6, 491-494; J. S. Kim, P. H. Ho, N. C. Greenham, and R. H. Friend, J. Appl. Phys., 2000, 88, 1073; Y. Cao, I. D. Parker, G. Yu, C. Zhang, and A. J. Heeger, Nature, 1999, 397, 414; Commission International de l'Éclairage: Measurement of LEDs, CIE publication 127; B. W. D'Andrade, S. R. Forrest, Adv. Mater., 2004, 16, 1585; B. W. D'Andrade, R. J. Holmes, and S. R. Forrest, Adv. Mater., 2004, 16, 624; K. Mullen, Edited, Electroluminescence-from Synthesis to Devices, Wiley-VCH, 2005 (in press); M. H. Lu, J. C. Sturm, J. Appl. Phys., 2002, 91, 5951. -
FIG. 13 shows the total external luminous efficiency (LEtotal,) and the total external power efficiency (PEtotal, lm/W) versus current density J (mA/cM2) for Type I devices with PEDOT:PSS as the HIL, PVK-SO3Li as the HTL and t-Bu-PBD-SO3Na as the EIL/ETL. -
FIG. 14 shows the total external luminous efficiency (LEtotal) and the total external power efficiency (PEtotal, MW) versus current density J (mA/cm2) for Type II devices with PEDOT:PSS as the HIL and PVK-SO3Li as the HTL and t-Bu-PBD-SO3Na as the EIL/ETL. As reflected in these Figures, Type I devices have LEtotal=21 cd/A and PEtotal=6 lm/W at J=23 mA/cm2 andType 11 devices have LEtotal=16 cd/A and PEtota=3 lm/W at J=12 mA/cm2.
Claims (33)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US11/366,186 US8076842B2 (en) | 2005-03-01 | 2006-03-01 | Multilayer polymer light-emitting diodes for solid state lighting applications |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US65783605P | 2005-03-01 | 2005-03-01 | |
US11/366,186 US8076842B2 (en) | 2005-03-01 | 2006-03-01 | Multilayer polymer light-emitting diodes for solid state lighting applications |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/680,084 Continuation-In-Part US7830085B2 (en) | 2003-10-06 | 2003-10-06 | White electrophosphorescence from semiconducting polymer blends |
Publications (2)
Publication Number | Publication Date |
---|---|
US20060202616A1 true US20060202616A1 (en) | 2006-09-14 |
US8076842B2 US8076842B2 (en) | 2011-12-13 |
Family
ID=36384513
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/366,186 Expired - Fee Related US8076842B2 (en) | 2005-03-01 | 2006-03-01 | Multilayer polymer light-emitting diodes for solid state lighting applications |
Country Status (4)
Country | Link |
---|---|
US (1) | US8076842B2 (en) |
JP (2) | JP5529382B2 (en) |
DE (1) | DE112006000495B4 (en) |
WO (1) | WO2006094101A1 (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050073245A1 (en) * | 2003-10-06 | 2005-04-07 | Xiong Gong | White electrophosphorescence from semiconducting polymer blends |
US20070273273A1 (en) * | 2006-05-23 | 2007-11-29 | Yu-Jin Kim | White organic electroluminescent device and method of manufacturing the same |
US20080145520A1 (en) * | 2006-12-04 | 2008-06-19 | Asahi Kasei Kabushiki Kaisha | Method for producing electronic device and coating solutions suitable for the production method |
WO2012028853A1 (en) * | 2010-09-02 | 2012-03-08 | Cambridge Display Technology Limited | Electroluminescent device |
US20180072908A1 (en) * | 2007-06-25 | 2018-03-15 | Samsung Electronics Co., Ltd. | Compositions and methods including depositing nanomaterial |
US10633582B2 (en) | 2006-03-07 | 2020-04-28 | Samsung Electronics Co., Ltd. | Compositions, optical component, system including an optical component, and other products |
Families Citing this family (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2005056628A2 (en) * | 2003-09-17 | 2005-06-23 | The Regents Of The University Of California | Methods and devices comprising soluble conjugated polymers |
JP5909314B2 (en) * | 2004-09-03 | 2016-04-26 | ザ リージェンツ オブ ザ ユニバーシティ オブ カリフォルニア | Methods and devices using soluble conjugated polymers |
JP2008512523A (en) * | 2004-09-03 | 2008-04-24 | ザ リージェンツ オブ ザ ユニバーシティ オブ カリフォルニア | Soluble conjugated polymer |
KR101445418B1 (en) * | 2007-02-19 | 2014-09-26 | 다이니폰 인사츠 가부시키가이샤 | Organic electroluminescence element |
JP2010177462A (en) * | 2009-01-29 | 2010-08-12 | Nihon Univ | Organic el device |
GB2469498B (en) * | 2009-04-16 | 2012-03-07 | Cambridge Display Tech Ltd | Polymer and polymerisation method |
US8716700B2 (en) * | 2009-10-29 | 2014-05-06 | E I Du Pont De Nemours And Company | Organic light-emitting diodes having white light emission |
US8674343B2 (en) * | 2009-10-29 | 2014-03-18 | E I Du Pont De Nemours And Company | Organic light-emitting diodes having white light emission |
US8716699B2 (en) * | 2009-10-29 | 2014-05-06 | E I Du Pont De Nemours And Company | Organic light-emitting diodes having white light emission |
US10028361B2 (en) * | 2012-01-25 | 2018-07-17 | Konica Minolta, Inc. | Evaluation method, evaluation device, evaluation program, recording medium, and manufacturing method for organic electroluminescence element |
JP6519108B2 (en) * | 2013-07-12 | 2019-05-29 | 住友化学株式会社 | Composition and light emitting device using the same |
KR101646214B1 (en) * | 2015-02-25 | 2016-08-05 | 경희대학교 산학협력단 | Organic light emitting device having excellent luminous efficiency |
EP3639013A4 (en) | 2017-06-16 | 2021-06-30 | Duke University | Resonator networks for improved label detection, computation, analyte sensing, and tunable random number generation |
CN107706318B (en) * | 2017-10-16 | 2020-06-26 | 深圳市华星光电半导体显示技术有限公司 | Electronic transmission layer ink-jet printing ink and preparation method thereof |
Citations (27)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4948843A (en) * | 1989-05-30 | 1990-08-14 | Eastman Kodak Company | Dye polymer/sol-gel composites |
US4950587A (en) * | 1988-09-02 | 1990-08-21 | Eastman Kodak Company | J-aggregating dye polymers as spectral sensitizers for silver halide photographic compositions |
US5409109A (en) * | 1994-07-11 | 1995-04-25 | Smith; Brian K. | Enclosed arrow quiver |
US5612221A (en) * | 1993-02-26 | 1997-03-18 | Dade Chemistry Systems Inc. | Avidin-binding fluorescing and quenching reagent for use in homogeneous assays |
US5869350A (en) * | 1991-02-27 | 1999-02-09 | The Regents Of The University Of California | Fabrication of visible light emitting diodes soluble semiconducting polymers |
US5881083A (en) * | 1997-07-03 | 1999-03-09 | The Regents Of The University Of California | Conjugated polymers as materials for solid state laser |
US5968762A (en) * | 1998-03-19 | 1999-10-19 | The University Of Connecticut | Method for detecting bacteria in a sample |
US5990479A (en) * | 1997-11-25 | 1999-11-23 | Regents Of The University Of California | Organo Luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes |
US6026902A (en) * | 1997-07-24 | 2000-02-22 | Bingham; Clarke S. | Method and apparatus for enhancing oil recovery |
US6083635A (en) * | 1994-05-06 | 2000-07-04 | Bayer Ag | Conductive coatings |
US6280933B1 (en) * | 1990-03-14 | 2001-08-28 | The Regents Of The University Of California | Multichromophore fluorescent probes using DNA intercalation complexes |
US20020009728A1 (en) * | 2000-01-18 | 2002-01-24 | Quantum Dot Corporation | Oligonucleotide-tagged semiconductor nanocrystals for microarray and fluorescence in situ hybridization |
US20020022689A1 (en) * | 2000-08-14 | 2002-02-21 | Menon Vinod P. | Process for preparation of water soluble polypyrrole |
US20020034747A1 (en) * | 2000-03-22 | 2002-03-21 | Bruchez Marcel P. | Methods of using semiconductor nanocrystals in bead-based nucleic acid assays |
US20020064680A1 (en) * | 1997-11-05 | 2002-05-30 | Hubert Spreitzer | Substituted poly(arylene vinylenes), method for producing the same, and their use in electroluminescent elements |
US20020150759A1 (en) * | 2001-03-16 | 2002-10-17 | Jones Robert M. | Fluorescent polymer superquenching-based bioassays |
US6476184B1 (en) * | 1998-09-03 | 2002-11-05 | Fraunhofer-Gesellschaft Zur Forderung Der Angewardten Forschung E.V. | Aromatic poly(1,3,4-heterodiazoles) for use in optical devices, especially electroluminescent components |
US20020177136A1 (en) * | 2000-08-23 | 2002-11-28 | Mcbranch Duncan W. | Peptide nucleic acid based molecular sensors for nucleic acids |
US20030054413A1 (en) * | 2001-08-23 | 2003-03-20 | Sriram Kumaraswamy | Bio-sensing platforms for detection and quantitation of biological molecules |
US20030059975A1 (en) * | 1999-12-21 | 2003-03-27 | Plastic Logic Limited | Solution processed devices |
US20030222250A1 (en) * | 2002-02-28 | 2003-12-04 | Che-Hsiung Hsu | Polymer buffer layers and their use in light-emitting diodes |
US6692663B2 (en) * | 2001-02-16 | 2004-02-17 | Elecon, Inc. | Compositions produced by solvent exchange methods and uses thereof |
US6743640B2 (en) * | 2000-05-08 | 2004-06-01 | Qtl Biosystems Llc | Fluorescent polymer-QTL approach to biosensing |
US6849869B1 (en) * | 1999-07-19 | 2005-02-01 | Dupont Displays, Inc. | Long lifetime polymer light-emitting devices with improved luminous efficiency and improved radiance |
US6869695B2 (en) * | 2001-12-28 | 2005-03-22 | The Trustees Of Princeton University | White light emitting OLEDs from combined monomer and aggregate emission |
US6872474B2 (en) * | 2001-11-09 | 2005-03-29 | Jsr Corporation | Light emitting polymer composition, and organic electroluminescence device and production process thereof |
US20050073245A1 (en) * | 2003-10-06 | 2005-04-07 | Xiong Gong | White electrophosphorescence from semiconducting polymer blends |
Family Cites Families (24)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3476855B2 (en) * | 1992-01-07 | 2003-12-10 | 株式会社東芝 | Organic EL device |
DE69724107T2 (en) | 1996-03-04 | 2004-06-24 | DuPont Displays, Inc., Santa Barbara | POLYFLUORENE AS MATERIALS FOR PHOTOLUMINESCENCE AND ELECTROLUMINESCENCE |
AU9111098A (en) | 1998-01-09 | 1999-07-26 | Minnesota Mining And Manufacturing Company | Enzyme-specific cleavable polynucleotide substrate and assay method |
GB9819417D0 (en) | 1998-09-07 | 1998-10-28 | Secr Defence | Reaction method |
CA2340905A1 (en) | 1999-05-05 | 2000-11-09 | The Regents Of The University Of California | Method for detecting biological agents |
ATE262551T1 (en) | 2000-04-11 | 2004-04-15 | Dupont Displays Inc | SOLUBLE POLY(ARYL-OXADIAZOLE) CONJUGATED POLYMERS |
WO2002071813A1 (en) * | 2001-03-02 | 2002-09-12 | The Trustees Of Princeton University | Double doped-layer, phosphorescent organic light emitting devices |
CA2442860C (en) | 2001-04-05 | 2011-02-01 | Mario Leclerc | Detection of negatively charged polymers using water-soluble, cationic, polythiophene derivatives |
GB0109108D0 (en) * | 2001-04-11 | 2001-05-30 | Cambridge Display Tech Ltd | Polymer, its preparation and uses |
JP2003077673A (en) * | 2001-06-19 | 2003-03-14 | Honda Motor Co Ltd | Organic electroluminescent element |
JP2003086376A (en) * | 2001-09-06 | 2003-03-20 | Nippon Hoso Kyokai <Nhk> | Organic electroluminescence device and its manufacturing method |
JP4007020B2 (en) | 2002-03-04 | 2007-11-14 | セイコーエプソン株式会社 | Droplet discharge device and driving method thereof, film forming device and film forming method, color filter manufacturing method, organic EL device manufacturing method, and electronic apparatus |
JP2003257647A (en) | 2002-03-05 | 2003-09-12 | Seiko Epson Corp | Organic el device manufacturing apparatus, organic el device, and electronic apparatus |
JP2004002703A (en) * | 2002-03-15 | 2004-01-08 | Sumitomo Chem Co Ltd | Polymeric compound and polymeric luminescent element using the same |
WO2004001379A2 (en) | 2002-06-20 | 2003-12-31 | The Regents Of The University Of California | Methods and compositions for detection and analysis of polynucleotides using light harvesting multichromophores |
KR100480442B1 (en) * | 2002-08-17 | 2005-04-06 | 한국과학기술연구원 | White organic light-emitting materials prepared by light-doping and electroluminescent devices using the same |
US7094902B2 (en) * | 2002-09-25 | 2006-08-22 | 3M Innovative Properties Company | Electroactive polymers |
SG111090A1 (en) | 2002-10-25 | 2005-05-30 | Agency Science Tech & Res | Cationic water-soluble conjugated polymers and their precursors |
US6982179B2 (en) * | 2002-11-15 | 2006-01-03 | University Display Corporation | Structure and method of fabricating organic devices |
US6967062B2 (en) * | 2003-03-19 | 2005-11-22 | Eastman Kodak Company | White light-emitting OLED device having a blue light-emitting layer doped with an electron-transporting or a hole-transporting material or both |
JP4736336B2 (en) * | 2003-03-26 | 2011-07-27 | コニカミノルタホールディングス株式会社 | Organic electroluminescence element, lighting device and display device |
JP4688424B2 (en) * | 2003-03-31 | 2011-05-25 | 三洋電機株式会社 | Organic electroluminescent device and manufacturing method thereof |
JP2004342407A (en) * | 2003-05-14 | 2004-12-02 | Fuji Photo Film Co Ltd | Organic electroluminescent element and its manufacturing method |
WO2005056628A2 (en) | 2003-09-17 | 2005-06-23 | The Regents Of The University Of California | Methods and devices comprising soluble conjugated polymers |
-
2006
- 2006-03-01 US US11/366,186 patent/US8076842B2/en not_active Expired - Fee Related
- 2006-03-01 WO PCT/US2006/007373 patent/WO2006094101A1/en active Application Filing
- 2006-03-01 JP JP2007558202A patent/JP5529382B2/en not_active Expired - Fee Related
- 2006-03-01 DE DE112006000495.6T patent/DE112006000495B4/en not_active Expired - Fee Related
-
2014
- 2014-02-19 JP JP2014029465A patent/JP5933606B2/en not_active Expired - Fee Related
Patent Citations (29)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4950587A (en) * | 1988-09-02 | 1990-08-21 | Eastman Kodak Company | J-aggregating dye polymers as spectral sensitizers for silver halide photographic compositions |
US4948843A (en) * | 1989-05-30 | 1990-08-14 | Eastman Kodak Company | Dye polymer/sol-gel composites |
US6280933B1 (en) * | 1990-03-14 | 2001-08-28 | The Regents Of The University Of California | Multichromophore fluorescent probes using DNA intercalation complexes |
US5869350A (en) * | 1991-02-27 | 1999-02-09 | The Regents Of The University Of California | Fabrication of visible light emitting diodes soluble semiconducting polymers |
US6534329B2 (en) * | 1991-02-27 | 2003-03-18 | The Regents Of The University Of California | Visible light emitting diodes fabricated from soluble semiconducting polymers |
US5612221A (en) * | 1993-02-26 | 1997-03-18 | Dade Chemistry Systems Inc. | Avidin-binding fluorescing and quenching reagent for use in homogeneous assays |
US6083635A (en) * | 1994-05-06 | 2000-07-04 | Bayer Ag | Conductive coatings |
US5409109A (en) * | 1994-07-11 | 1995-04-25 | Smith; Brian K. | Enclosed arrow quiver |
US5881083A (en) * | 1997-07-03 | 1999-03-09 | The Regents Of The University Of California | Conjugated polymers as materials for solid state laser |
US6026902A (en) * | 1997-07-24 | 2000-02-22 | Bingham; Clarke S. | Method and apparatus for enhancing oil recovery |
US20020064680A1 (en) * | 1997-11-05 | 2002-05-30 | Hubert Spreitzer | Substituted poly(arylene vinylenes), method for producing the same, and their use in electroluminescent elements |
US5990479A (en) * | 1997-11-25 | 1999-11-23 | Regents Of The University Of California | Organo Luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes |
US5968762A (en) * | 1998-03-19 | 1999-10-19 | The University Of Connecticut | Method for detecting bacteria in a sample |
US6476184B1 (en) * | 1998-09-03 | 2002-11-05 | Fraunhofer-Gesellschaft Zur Forderung Der Angewardten Forschung E.V. | Aromatic poly(1,3,4-heterodiazoles) for use in optical devices, especially electroluminescent components |
US6849869B1 (en) * | 1999-07-19 | 2005-02-01 | Dupont Displays, Inc. | Long lifetime polymer light-emitting devices with improved luminous efficiency and improved radiance |
US20030059975A1 (en) * | 1999-12-21 | 2003-03-27 | Plastic Logic Limited | Solution processed devices |
US20020009728A1 (en) * | 2000-01-18 | 2002-01-24 | Quantum Dot Corporation | Oligonucleotide-tagged semiconductor nanocrystals for microarray and fluorescence in situ hybridization |
US20020034747A1 (en) * | 2000-03-22 | 2002-03-21 | Bruchez Marcel P. | Methods of using semiconductor nanocrystals in bead-based nucleic acid assays |
US6743640B2 (en) * | 2000-05-08 | 2004-06-01 | Qtl Biosystems Llc | Fluorescent polymer-QTL approach to biosensing |
US20040241768A1 (en) * | 2000-05-08 | 2004-12-02 | Whitten David G. | Fluorescent polymer-QTL approach to biosensing |
US20020022689A1 (en) * | 2000-08-14 | 2002-02-21 | Menon Vinod P. | Process for preparation of water soluble polypyrrole |
US20020177136A1 (en) * | 2000-08-23 | 2002-11-28 | Mcbranch Duncan W. | Peptide nucleic acid based molecular sensors for nucleic acids |
US6692663B2 (en) * | 2001-02-16 | 2004-02-17 | Elecon, Inc. | Compositions produced by solvent exchange methods and uses thereof |
US20020150759A1 (en) * | 2001-03-16 | 2002-10-17 | Jones Robert M. | Fluorescent polymer superquenching-based bioassays |
US20030054413A1 (en) * | 2001-08-23 | 2003-03-20 | Sriram Kumaraswamy | Bio-sensing platforms for detection and quantitation of biological molecules |
US6872474B2 (en) * | 2001-11-09 | 2005-03-29 | Jsr Corporation | Light emitting polymer composition, and organic electroluminescence device and production process thereof |
US6869695B2 (en) * | 2001-12-28 | 2005-03-22 | The Trustees Of Princeton University | White light emitting OLEDs from combined monomer and aggregate emission |
US20030222250A1 (en) * | 2002-02-28 | 2003-12-04 | Che-Hsiung Hsu | Polymer buffer layers and their use in light-emitting diodes |
US20050073245A1 (en) * | 2003-10-06 | 2005-04-07 | Xiong Gong | White electrophosphorescence from semiconducting polymer blends |
Cited By (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050073245A1 (en) * | 2003-10-06 | 2005-04-07 | Xiong Gong | White electrophosphorescence from semiconducting polymer blends |
US10633582B2 (en) | 2006-03-07 | 2020-04-28 | Samsung Electronics Co., Ltd. | Compositions, optical component, system including an optical component, and other products |
US20070273273A1 (en) * | 2006-05-23 | 2007-11-29 | Yu-Jin Kim | White organic electroluminescent device and method of manufacturing the same |
US7867630B2 (en) * | 2006-05-23 | 2011-01-11 | Samsung Mobile Display Co., Ltd. | White organic electroluminescent device and method of manufacturing the same |
US20080145520A1 (en) * | 2006-12-04 | 2008-06-19 | Asahi Kasei Kabushiki Kaisha | Method for producing electronic device and coating solutions suitable for the production method |
US8101230B2 (en) * | 2006-12-04 | 2012-01-24 | Asahi Kasei Kabushiki Kaisha | Method for producing electronic device and coating solutions suitable for the production method |
US20180072908A1 (en) * | 2007-06-25 | 2018-03-15 | Samsung Electronics Co., Ltd. | Compositions and methods including depositing nanomaterial |
US11214701B2 (en) * | 2007-06-25 | 2022-01-04 | Samsung Electronics Co., Ltd. | Compositions and methods including depositing nanomaterial |
US11472979B2 (en) * | 2007-06-25 | 2022-10-18 | Samsung Electronics Co., Ltd. | Compositions and methods including depositing nanomaterial |
US11866598B2 (en) | 2007-06-25 | 2024-01-09 | Samsung Electronics Co., Ltd. | Compositions and methods including depositing nanomaterial |
WO2012028853A1 (en) * | 2010-09-02 | 2012-03-08 | Cambridge Display Technology Limited | Electroluminescent device |
GB2496562A (en) * | 2010-09-02 | 2013-05-15 | Cambridge Display Tech Ltd | Electroluminescent Device |
Also Published As
Publication number | Publication date |
---|---|
WO2006094101A1 (en) | 2006-09-08 |
JP5933606B2 (en) | 2016-06-15 |
US8076842B2 (en) | 2011-12-13 |
JP5529382B2 (en) | 2014-06-25 |
DE112006000495T5 (en) | 2008-02-14 |
DE112006000495B4 (en) | 2017-11-09 |
JP2008532322A (en) | 2008-08-14 |
JP2014131066A (en) | 2014-07-10 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US8076842B2 (en) | Multilayer polymer light-emitting diodes for solid state lighting applications | |
US7830085B2 (en) | White electrophosphorescence from semiconducting polymer blends | |
Misra et al. | White organic LEDs and their recent advancements | |
CN101461075B (en) | Organic light-emitting device with a phosphor-sensitized fluorescent emission layer | |
JP4493915B2 (en) | High efficiency multicolor electric field phosphorescent OLED | |
JP4895742B2 (en) | White organic electroluminescence device | |
US20030124381A1 (en) | White light emitting OLEDs from combined monomer and aggregate emission | |
Duggal et al. | Solution-processed organic light-emitting diodes for lighting | |
Najafabadi et al. | High-performance inverted top-emitting green electrophosphorescent organic light-emitting diodes with a modified top Ag anode | |
US20100096978A1 (en) | Light Emissive Device | |
Knauer et al. | Stacked inverted top-emitting green electrophosphorescent organic light-emitting diodes on glass and flexible glass substrates | |
JP2008508727A (en) | White light emitting electroluminescent device | |
Liu et al. | Efficient solution-processed blue phosphorescent organic light-emitting diodes with halogen-free solvent to optimize the emissive layer morphology | |
US8017251B2 (en) | Organic electroluminescent device | |
KR100721428B1 (en) | Organic light emitting diode and the method for preparing the same | |
KR100594775B1 (en) | White organic light emitting device | |
Drolet et al. | Red–green–blue light-emitting diodes containing fluorene-based copolymers | |
Petrova et al. | materials used for organic light-emitting diodes: organic electroactive compounds | |
TWI484858B (en) | Organic light emitting device having a transparent microcavity | |
Mullemwar et al. | OLEDs: Emerging technology trends and designs | |
Tomova et al. | Organic light-emitting diodes (OLEDs)–the basis of next generation light-emitting dеvices | |
KR100757780B1 (en) | Polymer-based electrophosphorescent devices by controlled morphology of emitting layer | |
CN107293645A (en) | A kind of white light top luminous organic diode and preparation method thereof | |
Pal et al. | Solution-processed light-emitting devices | |
US20050123803A1 (en) | Organic electroluminescence device |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA, CALIF Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:GONG, XIONG;HEEGER, ALAN J.;MOSES, DANIEL;AND OTHERS;SIGNING DATES FROM 20050921 TO 20051004;REEL/FRAME:017377/0071 Owner name: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA, CALIF Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:GONG, XIONG;HEEGER, ALAN J.;MOSES, DANIEL;AND OTHERS;REEL/FRAME:017377/0071;SIGNING DATES FROM 20050921 TO 20051004 |
|
ZAAA | Notice of allowance and fees due |
Free format text: ORIGINAL CODE: NOA |
|
ZAAB | Notice of allowance mailed |
Free format text: ORIGINAL CODE: MN/=. |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
CC | Certificate of correction | ||
FPAY | Fee payment |
Year of fee payment: 4 |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 8TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1552); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY Year of fee payment: 8 |
|
FEPP | Fee payment procedure |
Free format text: MAINTENANCE FEE REMINDER MAILED (ORIGINAL EVENT CODE: REM.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
LAPS | Lapse for failure to pay maintenance fees |
Free format text: PATENT EXPIRED FOR FAILURE TO PAY MAINTENANCE FEES (ORIGINAL EVENT CODE: EXP.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |
|
FP | Lapsed due to failure to pay maintenance fee |
Effective date: 20231213 |