Single-junction fullerene solar cells with 10% efficiency and high open-circuit voltage approaching 1 V

Abstract

It has been proven that the introduction of F atom and the replacement of alkyl side-chain with alkylthio substituent could be the effective side-chain strategies, to obtain the deep highest occupied molecular orbital (HOMO) energy level with little influence on the optical absorption, and in turn, the small photo energy loss (Eloss). In this work, we combine the advantages of D–A(π)–Q–A(π) strategy and the above side chain engineering, to construct a series of high-performance polymers P1-P3 with high open-circuit voltage (VOC) of exceeding 0.90V in the conventional solar cells. Meanwhile, small Elosss of 0.73–0.78eV are achieved accompanying high VOC and almost unchanged optical bandgaps of ~ 1.70eV, which are the smaller values in comparison with that of the other high-performance polymer systems. More encouragingly, P2-based solar cells exhibit high PCE of 10.30% and VOC of 0.97V, which is one of the highest values for polymer/fullerene based solar cells. Our work not only demonstrates a series of high-efficiency new materials, but also strongly confirms that the combination of D–A(π)–Q–A(π) arrangement and rational side chain engineering is a very promising strategy to construct high-performance photovoltaic polymers with reduced energy loss.