Nanomorphology and Charge Generation in Bulk Heterojunctions Based on Low-Bandgap Dithiophene Polymers with Different Bridging Atoms

Autor: Christoph J. Brabec, Markus C. Scharber, Kurt Hingerl, Russell Gaudiana, J Joachim Loos, Zenghuo Zhu, Gilles Dennler, Mauro Morana, Karen Forberich, David Waller, Hamed Azimi, SS Svetlana van Bavel, Hans-Joachim Egelhaaf, Jens Hauch
Přispěvatelé: Materials and Interface Chemistry
Rok vydání: 2010
Předmět:
Zdroj: Advanced Functional Materials, 20(7), 1180-1188. Wiley-VCH Verlag
ISSN: 1616-3028
1616-301X
DOI: 10.1002/adfm.200900931
Popis: Carbon bridged (C-PCPDTBT) and silicon-bridged (Si-PCPDTBT) dithiophene donor-acceptor copolymers belong to a promising class of low bandgap materials. Their higher field-effect mobility, as high as 10 -2 cm 2 V -1 s -1 in pristine films, and their more balanced charge transport in blends with fullerenes make silicon-bridged materials better candidates for use in photovoltaic devices. Striking morphological changes are observed in polymer:fullerene bulk heterojunctions upon the substitution of the bridging atom. XRD investigation indicates increased π-π stacking in Si-PCPDTBT compared to the carbon-bridged analogue. The fluorescence of this polymer and that of its counterpart C-PCPDTBT indicates that the higher photogeneration achieved in Si-PCPDTBT:fullerene films (with either [C60]PCBM or [C70]PCBM) can be correlated to the inactivation of a charge-transfer complex and to a favorable length of the donor-acceptor phase separation. TEM studies of Si-PCPDTBT:fullerene blended films suggest the formation of an interpenetrating network whose phase distribution is comparable to the one achieved in C-PCPDTBT-fullerene using 1,8-octanedithiol as an additive. In order to achieve a balanced hole and electron transport, Si-PCPDTBT requires a lower fullerene content (between 50 to 60 wt%) than C-PCPDTBT (more than 70 wt%). The Si-PCPDTBT:[C70]PCBM OBHJ solar cells deliver power conversion efficiencies of over 5%.
Databáze: OpenAIRE
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