Ternary small molecules organic photovoltaics exhibiting 12.84% efficiency

Abstract

Small molecules organic photovoltaics (SMPVs) were prepared with DR3TSBDT as donor, narrow band gap material Y6 and broad band gap material PC71BM as acceptor. The Y6 based binary SMPVs exhibit a power conversion efficiency (PCE) of 10.53%, with short-circuit current density (JSC) of 21.67 mA cm−2, open-circuit voltage (VOC) of 0.879 V and fill factor (FF) of 55.21%. A 12.84% PCE is achieved from the optimized ternary SMPVs with 40 wt% PC71BM in acceptors, which is attributed to the enhanced JSC of 22.19 mA cm−2 and FF of 67.27% resulting from the well-optimized phase separation with PC71BM as morphology regulator. Hollow spherical structure of PC71BM with high electron mobility may connect Y6 molecules to form the more continuous electron transport channels in ternary active layers. Meanwhile, DR3TSBDT molecular arrangement can be markedly adjusted by incorporating PC71BM to form 3D texture structure. The well-optimized phase separation degree and molecular arrangement in ternary active layers can well support the enhanced FFs of ternary SMPVs compared with that of binary SMPVs. Over 21% PCE improvement is achieved by employing ternary strategy with 40 wt% PC71BM in acceptors, the 12.84% PCE should be among the highest values of SMPVs.