Solid additive modulates acceptor crystallization to achieve 19.11% efficiency and high storage stability in organic solar cells

Abstract

Ideal nanoscale phase-separated morphology is the primary condition to obtain high photovoltaic conversion efficiency (PCE) and high stability of organic solar cells (OSCs). However, the differences in solubility, miscibility and crystallinity between donors and acceptors make it difficult to achieve the optimal active layer morphology of OSCs. Herein, the volatile solid additive 3,5-dibromotoluene (DTL) with strong electronegativity and dipole moment has been developed for OSCs. DTL can interact with the acceptor, modulating its crystallization and stacking, enhancing donor/acceptor miscibility, reducing trap density, inhibiting carrier recombination, and balancing charge transport. Notably, the introduction of DTL finely tunes the energy level of the acceptor, which greatly enhances the open-circuit voltage (VOC) of the device compared to the conventional additive 1,8-diiodooctane (DIO). As a result, the DTL-treated PM6: L8-BO-based OSCs obtained a high PCE of 18.87% and enhanced stability. Furthermore, the PM6: PM1: L8-BO+ DTL-based OSCs achieved a champion PCE of 19.11%. This work deepens the working mechanism of additive strategy for regulating the morphology and improving performance, providing an effective method for achieving high-performance OSCs.