Reverse crystallization regulation of donor and acceptor via green solid additive enabling 19.6% efficiency binary organic solar cells

Solid additives (SAs) have been proven as a useful strategy to finely tune the morphology of organic solar cells (OSCs). However, the most commonly used SAs are toxic and require high loading concentrations during fabrication, generating material waste and sustainability challenges. Here, we report a flavoring compound, 1,4-dithiane (DTA), as a green SA. It was found that DTA can interact synergistically with both the donor and acceptor. By inducing donor crystallization ahead of the acceptor, DTA creates a polymer network framework first. This framework guides the following crystallization of acceptor, thus leading to an optimized morphology in active layers. As a result, PM6:L8-BO binary devices processed with DTA achieve a power conversion efficiency (PCE) of 19.64% with a high fill factor (FF) of 81.1%, significantly surpassing the pristine device’s PCE of 18.48%. The confluence of high efficiency, enhanced eco-compatibility, and minimal additive dosage establishes DTA-mediated morphology control as a viable pathway toward commercial OSC technologies.