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Issue 41, 2012
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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

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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.

Graphical abstract: 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

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Article information


Submitted
25 May 2012
Accepted
09 Aug 2012
First published
09 Aug 2012

Phys. Chem. Chem. Phys., 2012,14, 14243-14248
Article type
Paper

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

L. Pandey, C. Doiron, J. S. Sears and J. Brédas, Phys. Chem. Chem. Phys., 2012, 14, 14243
DOI: 10.1039/C2CP41724C

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