J71-based ternary organic photovoltaics exhibiting 13.65% efficiency†
A series of organic photovoltaics (OPVs) were prepared by using J71 as the donor and non-fullerene materials, namely, BTP-BO-4Cl or ITIC or their mixture as the acceptor. The BTP-BO-4Cl- and ITIC-based binary OPVs exhibited power conversion efficiencies (PCEs) of 11.63% and 10.46%, respectively, resulting from the different open-circuit voltages (VOCs) of 0.881 V vs. 0.941 V, short-circuit current densities (JSCs) of 22.88 mA cm−2 vs. 15.39 mA cm−2 and fill factors (FFs) of 57.79% vs. 72.34%. Meanwhile, BTP-BO-4Cl and ITIC exhibited apparently complementary photon harvesting ranges, which were conducive to improving the photon harvesting of ternary active layers with different ITIC contents in the acceptors. An optimized PCE of 13.65% was achieved from the ternary OPVs with 60 wt% ITIC content in the acceptors, mainly benefiting from the markedly increased VOC and FF, compared with that for the BTP-BO-4Cl-based binary OPVs. Over 17% improvement in PCE was obtained by incorporating 60 wt% ITIC in the acceptors, indicating that the ternary strategy can be an efficient and simple method to improve the performance of OPVs.