Morphology optimization induced by a highly volatile solid additive contributes to efficient organic solar cells with enhanced photostability.

The morphology of the active layer plays a crucial role in the device performance and stability of organic solar cells (OSCs). To obtain the optimized blend film morphology, numerous solvent additives have been developed and utilized. Nevertheless, the commonly used high boiling point solvent additives have strict volume control and residual problems, which are not conducive to the development of OSCs. To alter the situation, it is urgent to develop highly volatile additives to minimize the unfavorable effect. Here, a volatile aromatic small molecule, benzoylacetate (BA), is used as a solid additive to control the morphology of the active layer during the post-treatment procedure. More importantly, BA has an apparent positive interaction with Y6, leading to more favorable molecular arrangement in the blend film and enhanced charge transfer properties. Finally, the BA-treated PM6:Y6 device exhibits improved device performance and photostability. Moreover, BA could be used as a universal solid additive for different OSC systems. Specifically, a superior PCE of 18.5 % is achieved in BA-processed PM6:L8-BO binary system with good photostability. Our work demonstrates an approach of applying a volatile solid additive to improve the device performance and photostability. [Display omitted] • High-performance organic solar cells (OSCs) were fabricated by introducing benzoylacetone (BA), a volatile aromatic small molecule, into the non-fullerene acceptor (NFA) systems. • The addition of BA can be used to control the blend morphology and obtain improved crystallinity and appropriate phase separation. Meanwhile, good volatility of BA is beneficial to improve the photostability of OSCs. • For the binary PM6:L8-BO device, a notable PCE of 18.5 % was yielded after treatment with the BA additive, which is much higher than that of the device treated with DIO. [ABSTRACT FROM AUTHOR]