Ultrafast charge transfer in operating bulk heterojunction solar cells.

Zhong, Chengmei; Choi, Hyosung; Kim, Jin Young; Woo, Han Young; Nguyen, Thanh Luan; Huang, Fei; Cao, Yong; Heeger, Alan J · Adv Mater · 2015

basic_science · Level V

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Abstract

The ultrafast charge generation process in organic solar cell devices is investigated by transient reflection spectroscopy on five state-of-the-art bulk heterojunction systems. The charge generation process in operating devices is found to be a combination of an ultrafast generation mechanism over several hundred femto-seconds and a slow process from pico-seconds to nanoseconds, limited by exciton diffusion dynamics. In addition, the lack of electric field dependence in the charge dynamics rules out geminate recombination as an important loss mechanism.