Skip to main content
Article
Persistent Dopants and Phase Segregation in Organolead Mixed-Halide Perovskites
Chemistry of Materials
  • Bryan A. Rosales, Iowa State University
  • Long Men, Iowa State University
  • Sarah D. Cady, Iowa State University
  • Michael P. Hanrahan, Iowa State University
  • Aaron J. Rossini, Iowa State University
  • Javier Vela, Iowa State University
Document Type
Article
Publication Version
Published Version
Publication Date
10-11-2016
DOI
10.1021/acs.chemmater.6b01874
Abstract
Organolead mixed-halide perovskites such as CH3NH3PbX3–aX′a (X, X′ = I, Br, Cl) are interesting semiconductors because of their low cost, high photovoltaic power conversion efficiencies, enhanced moisture stability, and band gap tunability. Using a combination of optical absorption spectroscopy, powder X-ray diffraction (XRD), and, for the first time, 207Pb solid state nuclear magnetic resonance (ssNMR), we probe the extent of alloying and phase segregation in these materials. Because 207Pb ssNMR chemical shifts are highly sensitive to local coordination and electronic structure, and vary linearly with halogen electronegativity and band gap, this technique can provide the true chemical speciation and composition of organolead mixed-halide perovskites. We specifically investigate samples made by three different preparative methods: solution phase synthesis, thermal annealing, and solid phase synthesis. 207Pb ssNMR reveals that nonstoichiometric dopants and semicrystalline phases are prevalent in samples made by solution phase synthesis. We show that these nanodomains are persistent after thermal annealing up to 200 °C. Further, a novel solid phase synthesis that starts from the parent, single-halide perovskites can suppress phase segregation but not the formation of dopants. Our observations are consistent with the presence of miscibility gaps and spontaneous spinodal decomposition of the mixed-halide perovskites at room temperature. This underscores how strongly different synthetic procedures impact the nanostructuring and composition of organolead halide perovskites. Better optoelectronic properties and improved device stability and performance may be achieved through careful manipulation of the different phases and nanodomains present in these materials.
Comments

Reprinted with permission from Chemistry of Materials 28 (2016): 6848, doi:10.1021/acs.chemmater.6b01874. Copyright 2016 American Chemical Society.

Copyright Owner
American Chemical Society
Language
en
File Format
application/pdf
Citation Information
Bryan A. Rosales, Long Men, Sarah D. Cady, Michael P. Hanrahan, et al.. "Persistent Dopants and Phase Segregation in Organolead Mixed-Halide Perovskites" Chemistry of Materials Vol. 28 (2016) p. 6848 - 6859
Available at: http://works.bepress.com/javier_vela-becerra/27/