Efficient and stable high-entropy organic photovoltaics

Abstract

The lack of simultaneous high efficiency and long-term stability in organic photovoltaics (OPVs) poses a major challenge to commercialization. Here, we introduce a high-entropy (HE) methodology by both physical blending and chemical synthesis, where multiple components are mixed to improve system entropy. Our findings show that physically blended HE blends maintained strong π–π interactions due to acceptors’ identical backbones. The different halogens or alkyl chains reduced structure order and fostered an optimal mixture, where a redistribution of the conduction-band density of states was found, leading to a higher effective band gap, reduced non-radiative recombination, and elevated open-circuit voltage. This HE design rule was then extended to chemical synthesis to make HE materials, which yielded a maximum power conversion efficiency of 20.6% (20.3% ± 0.2%, certified as 20.0%) in OPV devices. Moreover, both operational and thermal stability were improved, measured in conventional encapsulated devices under continuous illumination.