An A′–A–DA′D–A–A′-type acceptor enables organic solar cells with high VOC and low nonradiative voltage loss

Abstract

Reducing the voltage loss (ΔV_loss) and thus increasing the open-circuit voltage (V_OC) are key factors to further improve the photovoltaic performance of organic solar cells (OSCs). For A–DA′D–A-type acceptors, the above goals could be achieved through the regulation of the central A′ core and terminal groups. Hence, a novel A′–A–DA′D–A–A′ type acceptor named BTA79 was developed, where the benzotriazole (BTA) unit was used as the A′ unit on both the central core and the terminal groups. Two BTA-based polymers, J52 and J52-Cl, were used as donors to fabricate OSCs. A J52:BTA79-based device realized a power conversion efficiency of 10.71%, with a V_OC of 0.93 V and a nonradiative recombination voltage loss (ΔV_non-rad) of 0.23 V. Interestingly, the J52-Cl:BTA79 system showed a lower ΔV_non-rad of 0.18 V but an inferior efficiency of 2.48%. This design of the A′–A–DA′D–A–A′-type acceptor provides a key reference for the development of high V_OC acceptors for OSCs.