Two new tercopolymers incorporating electron-rich benzodithiophene and electron-accepting pyrrolo[3,4-c]pyrrole-1,3-dione and difluorobenzothiadiazole derivatives for polymer solar cells

Two new tercopolymers (RP1 and RP2) containing electron-donating benzodithiophene, weak electron-accepting pyrrolo[3,4-c]pyrrole-1,3-dione derivative and strong electron-accepting 5,6-difluorobenzothiadiazole derivative were prepared. The opto-electrical studies showed that RP1 and RP2 displayed identical optical band gaps (E_g ~ 1.72 eV) and highest occupied/lowest unoccupied molecular orbital energy levels (HOMO/LUMO ~ −5.32 eV/−3.60 eV). The polymer solar cells prepared with the configuration of ITO/PEDOT:PSS/RP1:PC₇₀BM (1:1.5 wt%) + 3 vol% DIO/Al and ITO/PEDOT:PSS/RP2:PC₇₀BM (1:1.5 wt%) + 3 vol% DIO/Al exhibited a maximum power conversion efficiency (PCE) of 5.16% (V_oc ~ 0.76 V, J_sc ~ 10.93 mA/cm², and FF ~ 0.62) and a PCE of 3.56% (V_oc ~ 0.67 V, J_sc ~ 9.67 mA/cm², and FF ~ 0.55), respectively.