Ternary organic photovoltaics with alloyed donor exhibiting 75.53% fill factor and 12.26% efficiency

Organic photovoltaics (OPVs) were fabricated with J71, PBT1-C or their blends as donor and IT-2F as acceptor. The power conversion efficiency (PCE) of J71 and PBT1-C based binary OPVs arrive to 10.45% and 10.23%, respectively. Although the very similar photovoltaic performance of two binary OPVs, three photovoltaic parameters are distinctly different. Meanwhile, three materials also exhibit complementary absorption range to cover solar light as wide as possible. Integrating the advantages of materials and binary OPVs, the optimized ternary OPVs are obtained with 12.26% PCE and 75.53% fill factor by incorporating 20 wt% PBT1-C in donors. The enhanced photovoltaic performance should result from enhanced photon harvesting and optimized phase separation. The two polymer donors should prefer to form alloyed state, which can reasonably interpret the enhanced photovoltaic performance of ternary OPVs with PBT1-C content from 10 wt% to 50 wt% in donor.