Recent progress in minimizing the loss channel via triplet excitons in nonfullerene-based organic solar cells

Abstract

Low-lying triplet excitons, which are formed via charge back transfer from the triplet charge transfer state (³CT), represent an important loss channel in organic solar cells (OSCs), hindering further improvements in their photovoltaic performance. To date, there are three successful ways to minimize this loss channel: (1) manipulating the energetic landscape of OSCs; (2) suppressing the non-geminate recombination during charge transport; (3) facilitating intersystem conversion from ³CT to ¹CT via spin manipulation. In order to further minimize the loss channel, novel narrow bandgap NFAs with high triplet energy levels, new photovoltaic materials with high dielectric constants and charge mobilities, as well as new spin manipulating additives, are promising methods, which are enough to enable power conversion efficiencies of 22.15% with the current best device-performance metrics.