Fullerene derivative acceptors for high performance polymer solar cells

Abstract

Polymer solar cells (PSCs) are composed of a blend film of a conjugated polymer donor and a soluble fullerene derivative acceptor sandwiched between a PEDOT : PSS coated ITO positive electrode and a low workfunction metal negative electrode. The conjugated polymer donor and the fullerene derivative acceptor are the key photovoltaic materials for high performance PSCs. For the acceptors, although [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₀BM) and its corresponding C₇₀ derivative PC₇₀BM are dominantly used as the acceptors in PSC at present, several series of new fullerene derivatives with higher-lying LUMO energy level and better solubility were reported in recent years for further improving the power conversion efficiency of the PSCs. In this perspective paper, we reviewed the recent research progress on the new fullerene derivative acceptors, including various PC₆₀BM-like C₆₀ derivatives, PC₆₀BM bisadduct, PC₇₀BM bisadduct, indene-C₆₀ bisadduct and indene-C₇₀ bisadduct, trimetallic nitride endohedral fullerenes and other C₆₀ derivatives with multi side chains. The synthesis and physicochemical properties of PC₆₀BM and PC₇₀BM were also introduced considering the importance of the two fullerene acceptors.