Dopant-free, hole-transporting polymers containing benzotriazole acceptor unit for perovskite solar cells

Dopant-free, electron donor (D)–acceptor (A) type, polymeric hole-transporting materials (HTMs) possess excellent film formability and hole transport properties, which ensure high efficiency, stability, and reproducibility to the PVSCs. Compared with benzothiadiazole (BT), benzotriazole (BTA) was less incorporated into polymeric HTMs. Herein, two indacenodithieno[3,2-b]thiophene (IDTT)-BTA copolymers BT-T and BT-TT containing different π-bridge of thiophene and thienothiophene, are synthesized and studied. BT-T bearing thiophene π-bridge presents decent coplanarity, higher hole mobility, and better interface morphology than its sister polymer BT-TT. The PVSC with dopant-free BT-T displayed a peak power conversion efficiency (PCE) of 17.1% and remained above 85% of its initial PCE for more than 30 days at ambient conditions. In view of the rare report on the BTA-based polymeric HTMs, this work will cast lights on further exploration of high-efficiency D-A polymeric HTMs.