Efficient polymer solar cells based on terpolymers with a broad absorption range of 300–900 nm
Three novel random conjugated terpolymers were designed and synthesized by copolymerizing a benzo[1,2-b:4,5-b′]dithiophene (BDT) donor with an electron-deficient diketopyrrolo[3,4-c]pyrrole (DPP) unit and a thiophene-vinylene-dithienyl-benzothiadiazole (TVDTBT) side group into a polymer backbone. By tuning the ratio of DPP and TVDTBT in the terpolymers, the optical properties and energy levels of these random terpolymers could be rationally controlled. As a result, the terpolymers exhibited a very broad absorption range of 300–900 nm with a high absorption coefficient and deep HOMO energy levels. Bulk heterojunction polymer solar cells fabricated from P3 and PC61BM exhibited a promising power conversion efficiency of 5.29% without any processing additives.