Highly Efficient All‐Polymer Solar Cells Processed from Nonhalogenated Solvents

Abstract The remarkable advance of all‐polymer solar cells (all‐PSCs) achieved in the past decades is primarily powered by the innovation of polymer acceptors. However, most of high‐performance all‐PSCs are dominantly fabricated with halogenated solvents, which are detrimental to human bodies and the environment. Herein, eco‐friendly solvent‐processed all‐PSCs were developed, based on wide‐bandgap polymer poly[4,8‐bis(5‐(2‐ethylhexylthio)thiophen‐2‐yl)‐benzo‐[1,2‐b;4,5‐b’]dithiophene‐alt‐2,5‐di(butyloctylthiophen‐2‐yl) ‐thiazolo[5,4‐d]thiazole] (PSTZ) as donor and newly synthesized narrow‐bandgap polymer 5,6‐dicyano‐2,1,3‐benzothiadiazole indacenodithiophene (DCNBT‐IDT) as acceptor. When processed with o‐xylene and THF, PSTZ : DCNBT‐IDT‐based all‐PSCs yielded remarkable power conversion efficiencies of 7.23 and 8.77 % with high short‐circuit currents of 12.94 and 14.12 mA cm−2, respectively. The results indicated that the utilization of an all‐polymer blend based on narrow polymer acceptor and compatible polymer donor is an effective strategy for advancing eco‐friendly solvent‐processed all‐PSCs.