The alloy donor strategy leverages both complementary polymer donors to enable highly efficient and stable ternary organic solar cells

Abstract

Herein, organic photovoltaics (OPVs) were fabricated using J71 and PBDTTS-2FQx as donors and IT-4F as the acceptor. Binary devices based on J71:IT-4F and PBDTTS-2FQx:IT-4F achieved power conversion efficiencies (PCEs) of 9.52% and 6.44%, respectively. By leveraging the advantages of these two systems, a ternary OPV with both donors was successfully prepared. When a weight ratio of J71:PBDTTS-2FQx:IT-4F is 0.85:0.15:1, the ternary OPV achieved an optimum PCE of 11.23%, along with improved short-circuit current density (JSC) and fill factor (FF). The ternary OPVs also exhibited significantly enhanced stability compared to binary ones. Unencapsulated J71:IT-4F OPV retained only 80% of their initial PCE after 530 hours, while the unencapsulated ternary OPV maintained 80% efficiency after 1000 hours. This improvement is attributed to the good compatibility between J71 and BDTTS-2FQx, which promotes the formation of an alloy-like donor phase.