A non-fullerene all small molecule solar cell constructed with a diketopyrrolopyrrole-based acceptor having a power conversion efficiency higher than 9% and an energy loss of 0.54 eV

Abstract

The synthesis of a new symmetrical A–D–π–A–D–π–A non-fullerene small molecule acceptor MPU3 is reported. MPU3 consists of a diketopyrrolopyrrole (DPP) central acceptor core coupled to terminal dicyanorhodanine acceptors via a thiophene donor and an ethynyl linker. The optical and electrochemical properties of this compound were investigated. MPU3 showed strong absorption in the 600–850 nm range with an optical bandgap of 1.52 eV and the material was used as an acceptor for the fabrication of solution-processed bulk heterojunction organic solar cells using an A–D–π–A–D–π–A small molecule donor (SMD) consisting of a 5,10-dihydroindolo[3,2-b]indole (DINI) central donor core and benzothiadiazole (BT) acceptor units. This donor has a complementary absorption profile to MPU3. The organic solar cell based on an optimized an SMD:MPU3 active layer afforded overall power conversion efficiencies as high as 9.05%, which is higher than that obtained with an organic solar cell using PC₇₁BM as the acceptor (5.80%) fabricated under identical conditions. Interestingly, the energy loss in the organic solar cell based on SMD:MPU3 is very low, 0.54 eV, when compared to its SMD:PC₇₁BM counterpart (1.02 eV). Low energy loss is an essential feature to achieve high PCE values in organic solar cells.