Driving Force Dependence of Electron Transfer Kinetics and Yield in Low-Band-Gap Polymer Donor鈥揂cceptor Organic Photovoltaic Blends

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• 作者：Brendan F. Wright ; Kenji Sunahara ; Akihiro Furube ; Andrew Nattestad ; Tracey M. Clarke ; Guillermo C. Bazan ; Jason D. Azoulay ; Attila J. Mozer
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：June 11, 2015
• 年：2015
• 卷：119
• 期：23
• 页码：12829-12837
• 全文大小：466K
• ISSN：1932-7455

文摘

The rate of photoinduced electron transfer (PET) (魏_PET), quantum yield of PET (QY_PET), and charge extraction yield (EQE) are determined for a series of donor鈥揳cceptor (DA) organic photovoltaic systems, comprising low-band-gap polymer donors and the phenyl-C₆₁-butyric acid methyl ester (PCBM) acceptor. The energetic alignment of these polymer donors relative to PCBM provides driving forces for PET (螖G_PET) in the range of 0.18鈥?.57 eV. Femtosecond transient absorption (TA) spectroscopy was used to assess the PET kinetics and QY_PET, while time-resolved charge extraction (TRCE) measurements were employed to assess EQE. Near unity QY_PET was observed in DA blend films with a 螖G_PET of 0.57 and 0.30 eV, whereas no resolvable PET was observed with a 螖G_PET of 0.18 eV. For the DA blends that exhibit PET, both 魏_PET and QY_PET appear independent of 螖G_PET, with an average 魏_PET of 420 fs for the 70% PCBM blends. An increase in nanosecond charge separation yield (TA) and EQE (TRCE) between DA systems was observed, which appears not to be due to the PET process but rather the subsequent recombination processes. DA systems should be designed to minimize 螖G_PET, minimizing associated losses in device open-circuit potential; however, picosecond bimolecular recombination severely limits achievable charge extraction yields in these DA systems.