Efficient pyrrolo[3,4-c]pyrrole-1,3-dione-based wide band gap polymer for high-efficiency binary and ternary solar cells

Abstract

Wide band gap pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione (PPD)-based alternating polymer, P(BDTT-ttPPD) was synthesized by combining electron-rich 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDTT) and electron-deficient 4,6-bis(2-bromothieno[3,2-b]thiophen-5-yl)-5-octyl-2-(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,3(2H, 5H)-dione (ttPPD). When the P(BDTT-ttPPD) polymer was applied to binary polymer solar cells (PSCs) as a donor material, the device exhibited a maximum power conversion efficiency (PCE) of 6.93% with an open-circuit voltage (Voc) of 0.87 V, a short-circuit current (Jsc) of 11.38 mA/cm2, and a fill factor (FF) of 70%. The photovoltaic performance was further improved to 9.08% (Voc ∼ 0.80 V, Jsc ∼ 16.05 mA/cm2, and FF ∼ 71%) when the polymer was used as a donor component for absorbing high-energy light in ternary PSCs with a blend of P(BDTT-ttPPD):PTB7-Th:PC70BM. The overall PCE of ternary PSCs was found to be higher than those of the binary PSCs made form P(BDTT-ttPPD) or PTB7-Th. We discuss the property modulation of PPD-based polymers via the replacement of thiophene π–spacer units with thieno[3,2-b]thiophene.