Pyrrolo[3,2-b]pyrrole based small molecules as donor materials for OPVs

Abstract

A new accepter unit, pyrrolo[3,2-b]pyrrole-2,5-dione, deserves much attention as the electron-deficient unit for the generation of electron donor material for organic photovoltaic cells (OPVs). Pyrrolo[3,2-b]pyrrole-2,5-dione unit, regioisomer of the known pyrrolo[3,4-c]pyrrole-1,4-dione, is originated from the structure of stable synthetic pigment. The organic low band gap molecules with pyrrolo[3,2-b]pyrrole-2,5-dione, thiophene and triphenyl amine units were synthesized using Suzuki polymerization to generate SM-B, SM-M and SM-H. The spectrum of SM-B as the solid thin film shows absorption band with maximum peaks at 356 and 517nm, and the absorption onset at 667nm, corresponding to band gap of 1.86eV. The device comprising SM-B and PC71BM (1:4) showed a VOC of 0.79V, a JSC of 6.04mA/cm2, and a FF of 0.33, giving a power conversion efficiency of 1.56%.