Ternary organic solar cells with J71 as donor and alloyed acceptors exhibiting 13.16% efficiency

A series of organic solar cells (OSCs) were prepared with J71 as donor and IT-4F, T6Me or T6Me:IT-4F as acceptor(s), respectively. The two binary OSCs exhibit the same open circuit voltage (V_OC), complementary short circuit current density (J_SC) and fill factor (FF). The same V_OC of binary OSCs with J71 as donor indicate the similar lowest unoccupied molecular orbits (LUMO) levels of IT-4F and T6Me. Meanwhile, IT-4F and T6Me have complementary photon harvesting range, exhibiting great potential in preparing efficient ternary OSCs. The optimized ternary OSCs exhibit a 13.16% power conversion efficiency (PCE) with 50 wt% IT-4F in acceptors, resulting from the enhanced J_SC and FF. The FFs of ternary OSCs can be gradually improved along with IT-4F content increase, indicating that the two acceptors may prefer to form an alloyed state. The alloyed state of two acceptors should be beneficial to Förster energy transfer from IT-4F to T6Me, providing another channel for improving exciton utilization efficiency. This work indicates that alloyed model should have great potential in preparing efficient ternary OSCs with large content of the third component by fully exerting the advantages of used materials.