A new benzotriazole-containing wide bandgap D1–D′A–D2 conjugated polymer for air-processed ternary organic solar cells with efficiency approaching 17%

Abstract

In this report, we have designed a wide bandgap D1–(DA′)–D2 polymer, denoted as P154, based on BDT with thiazole side chains, a D1 thiophene donor unit, and a thieno[3,2-b]pyrrolobenzotriazole (TPBTA) (DA′) acceptor unit, which exhibit a dipole moment of 1.52 D and a deep highest occupied molecular orbital (HOMO) energy level of −5.38 eV. Employing the narrow bandgap non-fused asymmetric non-fullerene acceptor NFA-4, the optimized air-processed OSCs based on the P154 : NFA-4 active layer showed a power conversion efficiency (PCE) of 15.15%, which is superior to that of the PBDB-T : NFA-4 counterpart fabricated under identical conditions (12.86%). The higher PCE for the P154 : NFA-4 relative to PBDB-T : NFA-4 is attributed to the increased value of the short circuit current (J_SC), open circuit voltage (V_OC), and fill factor (FF), which are linked to the fact that the exciton diffusion and its subsequent dissociation in the former device are more effective than that for the latter device. When an optimal amount of P154 is incorporated into the PBDB-T : NFA-4 blend, the corresponding ternary OSCs exhibit a PCE of 16.96%, which is higher than that of the binary BHJ counterparts. The enhancement in the PCE for ternary OSCs is associated with balanced charge transport, a prolonged charge carrier lifetime, and faster extraction of charge carriers.