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

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 517 nm, and the absorption onset at 667 nm, corresponding to band gap of 1.86 eV. The device comprising SM-B and PC71BM (1:4) showed a VOC of 0.79 V, a JSC of 6.04 mA/cm2, and a FF of 0.33, giving a power conversion efficiency of 1.56%.