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Lowest Excited States and Optical Absorption Spectra of Donor-Acceptor Copolymers for Organic Photovoltaics: A New Picture Emerging From Tuned Long-Range Corrected Density Functionals
Physical Chemistry Chemical Physics (2012)
  • Laxman Pandey, Georgia Institute of Technology
  • Curtis Doiron, Georgia Institute of Technology
  • John S. Sears, Georgia Institute of Technology
  • Jean-Luc Brédas, Georgia Institute of Technology
Abstract
Polymers with low optical gaps are of importance to the organic photovoltaics community due to their potential for harnessing a large portion of the solar energy spectrum. The combination along their backbones of electron-rich and electron-deficient fragments contributes to the presence of low-lying excited states that are expected to display significant charge-transfer character. While conventional hybrid functionals are known to provide unsatisfactory results for charge-transfer excitations at the time-dependent DFT level, long-range corrected (LRC) functionals have been reported to give improved descriptions in a number of systems. Here, we use such LRC functionals, considering both tuned and default range-separation parameters, to characterize the absorption spectra of low-optical-gap systems of interest. Our results indicate that tuned LRC functionals lead to simulated optical-absorption properties in good agreement with experimental data. Importantly, the lowest-lying excited states (excitons) are shown to present a much more localized nature than initially anticipated.
Keywords
  • Optical absorption spectra,
  • Donor-acceptor copolymers,
  • Organic photovoltaics
Disciplines
Publication Date
2012
Citation Information
Laxman Pandey, Curtis Doiron, John S. Sears and Jean-Luc Brédas. "Lowest Excited States and Optical Absorption Spectra of Donor-Acceptor Copolymers for Organic Photovoltaics: A New Picture Emerging From Tuned Long-Range Corrected Density Functionals" Physical Chemistry Chemical Physics Vol. 14 Iss. 14243 (2012)
Available at: http://works.bepress.com/laxman_pandey/2/