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Proceedings Paper

Charge generation in organic solar cell materials studied by terahertz spectroscopy
Author(s): M. Scarongella; J. C. Brauer; J. D. Douglas; J. M. J. Fréchet; N. Banerji
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Paper Abstract

We have investigated the photophysics in neat films of conjugated polymer PBDTTPD and its blend with PCBM using terahertz time-domain spectroscopy. This material has very high efficiency when used in organic solar cells. We were able to identify a THz signature for bound excitons in neat PBDTTPD films, pointing to important delocalization in those excitons. Then, we investigated the nature and local mobility (orders of magnitude higher than bulk mobility) of charges in the PBDTTPPD:PCBM blend as a function of excitation wavelength, fluence and pump-probe time delay. At low pump fluence (no bimolecular recombination phenomena), we were able to observe prompt and delayed charge generation components, the latter originating from excitons created in neat polymer domains which, thanks to delocalization, could reach the PCBM interface and dissociate to charges on a time scale of 1 ps. The nature of the photogenerated charges did not change between 0.5 ps and 800 ps after photo-excitation, which indicated that the excitons split directly into relatively free charges on an ultrafast time scale.

Paper Details

Date Published: 9 September 2015
PDF: 13 pages
Proc. SPIE 9567, Organic Photovoltaics XVI, 95670M (9 September 2015); doi: 10.1117/12.2187473
Show Author Affiliations
M. Scarongella, Univ. of Fribourg (Switzerland)
Ecole Polytechnique Fédérale de Lausanne (Switzerland)
J. C. Brauer, Univ. of Fribourg (Switzerland)
J. D. Douglas, Univ. of California, Berkeley (United States)
J. M. J. Fréchet, Univ. of California, Berkeley (United States)
King Abdullah Univ. of Science and Technology (Saudi Arabia)
N. Banerji, Univ. of Fribourg (Switzerland)

Published in SPIE Proceedings Vol. 9567:
Organic Photovoltaics XVI
Zakya H. Kafafi; Paul A. Lane; Ifor D. W. Samuel, Editor(s)

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