Solid Additive Enables Organic Solar Cells with Efficiency up to 18.6

Additive strategies play a critical role in improving the performance of organic solar cells (OSCs). There are only a few reports on the application of solid additives for OSCs, which leaves a large space for further improvement of solid additives and further study on the relationship between material structure and property. PM6:BTP-eC9-based organic solar cells (OSCs) were prepared by using a small molecule BTA3 as a solid additive, and a high energy conversion efficiency of 18.65% is achieved. BTA3 has good compatibility with the acceptor component (BTP-eC9) and optimizes the morphology of the thin films. Moreover, the introduction of a small amount of BTA3 (5 wt %) effectively promotes exciton dissociation and charge transfer and suppresses charge recombination, and the relationship between the BTA3 content and the device parameter is deeply revealed. The use of BTA3 in the active layers is an attractive and effective strategy for high-performance OSCs.