The effect of the intramolecular disorder on hot exciton dynamics in polymer solar cells

In polymer solar cells (PSCs), the contribution of hot excitons to charge generation is strongly limited by their relatively low yield and ultrafast internal conversion (IC) process. In recent years, different strategies have been proposed to modulate the hot exciton dynamics, but a direct correlation between the microscopic properties of the polymer and hot exciton dynamics is still not completely clear. Here, we theoretically investigate the effect of intramolecular disorder, including the diagonal disorder (DD) and off-diagonal disorder (ODD), on the hot exciton dynamics based on the tight-binding model calculations. We find that the effect of ODD on the hot exciton yield is more significant than that of DD. In addition, we find that the IC relaxation time of hot excitons depends nonmonotonically on the intensity of DD and ODD, indicating that the intramolecular disorder can modulate the competitive relationship between the spontaneous dissociation of hot excitons and the IC process. This work provides a guide for promoting charge generation in PSCs dominated by hot exciton dissociation.

Automated summary

In this study, the effects of intramolecular disorder on hot exciton dynamics in polymer solar cells are investigated. It is found that off-diagonal disorder has a more significant impact on hot exciton yield compared to diagonal disorder. Furthermore, the intensity of both disorder types has a nonmonotonic relationship with the relaxation time of hot excitons, indicating that intramolecular disorder can modulate the competition between hot exciton dissociation and internal conversion processes. This research provides guidance for enhancing charge generation in polymer solar cells dominated by hot exciton dissociation.