Conjugated polymer donor with alkylthio-thiophene π-bridge for efficient polymer solar cells

A new conjugated polymer donor with alkylthio-substituted thiophene as p-bridge (namely PBZ-TS) is developed to further exploit the capability of alkylthio chains in designing high-performance donor materials. PBZ-TS possesses a broad absorption feature, a low-lying HOMO level, and high crystallinity. The polymer solar cell devices based on PBZ-TS:m-ITIC demonstrate high open-circuit voltage (V-OC) of 0.93 V. Especially, relative to the PBZ-TS: m-ITIC (1: 1, w/w) based binary device, an enhanced power conversion efficiency (PCE) of 8.66% is achieved from the PBZ-TS: m-ITIC: PC71BM (1:0.6:0.4, w/w) based ternary device resulting from the suppressed carrier recombination of binary blends. The results demonstrate that using alkylthio-substituted thiophene as pi-bridge is an effective strategy to down-shift HOMO level and increase V-OC of the polymer donor materials for PSCs.