Performance Enhancement of Ternary Polymer Solar Cells Induced by Tetrafluorotetracyanoquinodimethane Doping

Molecular electrical doping has been proved as an effective strategy to improve the performance of traditional binary polymer solar cells (PSCs). However, its effectiveness is not demonstrated yet in ternary PSCs which have recently emerged as a promising technique for organic photovoltaics. In this report, we investigate tetrafluorotetracyanoquinodimethane doping of a ternary PSC composed of one donor polymer and dual acceptors. It is found that an ion pair forms between the dopant and donor polymer, leading to the increase in conductivity, hole density, and hole mobility. By employing a low doping concentration of 0.1%, the power conversion efficiency of the ternary PSC is improved, mainly contributed by enhancements of the short-circuit current density (J(sc)) and fill factor (FF). Investigation of charge transport processes and kinetics reveals that J(sc) and FF improvements are ascribed to more efficient charge extraction, restrained nongeminate charge recombination, and optimized microstructure in doped ternary PSCs.