Regioisomer effects of [70]fullerene mono-adduct acceptors in bulk heterojunction polymer solar cells

Abstract

Despite numerous organic semiconductors being developed during the past decade, C₇₀ derivatives are predominantly used as electron acceptors in efficient polymer solar cells (PSCs). However, as-prepared C₇₀ mono-adducts intrinsically comprise regioisomers that would mask individual device performances depending on the substituent position on C₇₀. Herein, we separate the regioisomers of C₇₀ mono-adducts for PSC applications for the first time. Systematic investigations of the substituent position effect using a novel symmetric C₇₀ mono-adduct ([70]NCMA) and a prevalent, high-performance one ([70]PCBM) reveals that we can control the structures of the blend films with conjugated polymers and thereby improve the PSC performances by regioisomer separation. Our approach demonstrates the significance of exploring the best-matching regioisomer of C₇₀ mono-adducts with high-performance conjugated polymers, which would achieve a remarkable progress in PSC devices.