Enhanced dissociation of excitons and charge transfer in organic solar cells of polymer: Fullerene blends with molecular BPFZn doping

초록

We introduce bis(pentafluorophenyl)zinc (BPFZn) as a molecular dopant in an organic solar cell (OSC) system based on polymer:fullerene blends to improve the efficiency of exciton dissociation and balance charge-carrier mobilities. We employ PC71BM as an acceptor along with PTB7-Th as a donor to form bulk heterojunctions. The maximum power conversion efficiency increases from 7.7% without doping to 8.7% upon BPFZn doping at a concentration of 0.01 wt %. The fill factor, which is increased from 50.7% to 57.8%, is the main device parameter of enhancement. An optimal concentration of BPFZn promotes splitting of exciton and suppresses charge recombination in the PTB7-Th:PC71BM OSCs. Additionally, balanced carrier mobilities are observed in the moderately doped blends.

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