Thickness insensitive polymer solar cells employing D-A1-D-A2 random terpolymers based on different thiophene units as electron-donor

Abstract

Abstract A series of D-A1-D-A2 random polymers PTPDBTO-T, PTPDBTO-TT and PTPDBTO-3T, based on three different electron-donor units (D) (thiophene (T), thieno[3,2-b]thiophene (TT) and terthiophene (3T)) and two electron-accept units (A1 and A2) were synthesized and characterized for thickness insensitive polymer solar cells (PSCs). Three D units (T, TT and 3T) had a remarkable effect on the optical physics properties, solution process ability, and charge carrier transport of the resultant polymers, which in turn influenced their photovoltaic performances. It was observed that the absorption coefficient of PTPDBTO-TT was higher than that of PTPDBTO-T or PTPDBTO-3T. As a result, the random polymer PTPDBTO-TT based PSCs obtained power conversion efficiency (PCE) of 6.92% and fill factor (FF) of 61% at a thick active layer of 285 nm. The devices based on PTPDBTO-T afforded PCE of 6.37% and FF of 62% with an active layer thickness of 183 nm. Moreover, the photovoltaic performance of PSCs based on PTPDBTO-T and PTPDBTO-TT was insensitive to active layer thickness. Specifically, their PCEs were basically over 6% and FFs over 60% when the active layer thicknesses were tuned within 100–280 nm.