Structural-Evolution Dynamics and Structural-Defect Suppression in High-Efficiency All-Polymer Solar Cells via Dilution Effect

Abstract

Structural defects in organic solar cells (OSCs) can significantly impact their performance by altering the density of the trap states and disrupting the energy-level alignment. These defects are primarily formed during the film-formation process, serving as intrinsic traps. In this study, we employed a dilution approach by blending an insulating polymer, polystyrene (PS), to control the structural-evolution process and reduce structural defects. By incorporating PS into two all-polymer systems, namely, PBDB-T:N2200 and PM6:PY-IT, the presence of enhanced stack ordering led to a reduction in structural defects, thus facilitating the charge-transfer process in all-polymer OSCs. However, this phenomenon was not observed in the nonfullerene system PM6:BTP-eC9. The compatibility between various components was examined in solution using both experiments and theoretical simulations, which revealed better miscibility between PS and the polymer materials. Our study demonstrates that the dilution effect of insulating polymers can effectively regulate the structural-evolution process and defects in organic semiconductors, resulting in enhanced performance of organic electronic devices.