Efficient Ternary Polymer Solar Cells with Two Structurally Similar Fullerene-Free Acceptors to Redshift Absorption Peaks and Improve Exciton Dissociation

In this work, Y6 and BTP-eC9 blends are used as a acceptor and D18-Cl as donor to construct ternary PSCs and to boost the power conversion efficiency (PCE) of ternary polymer solar cells (PSCs). Compared with Y6, BTP-eC9 shows a red-shifted absorption peak. As a result, the optimized ternary PSCs show the highest short-circuit current density (JSC). Compared with Y6, BTP-eC9 shows a shallower LUMO level and paly the role of broaden energy level difference. Thus, the blend acceptor endows a high open-circuit voltage (VOC) to the ternary PSCs. In addition, the of Y6 and BTP-eC9 blend as acceptors to enhance crystalline and improve surface and bulk morphology of ternary films, which favor the enhancement of charge carrier mobility and suppression of charge carrier recombination. Thus, the blend of two acceptors with similar molecular structures boosts a higher photovoltaic performance than binary PSCs.