Intrinsic Role of Volatile Solid Additive in High-Efficiency PM6:Y6 Series Nonfullerene Solar Cells.

Organic nonfullerene solar cells (ONSCs) have made unprecedented progress, however, morphology optimization of ONSCs has been proven to be particularly challenging relative to classical fullerene-based devices. In this work, we report a novel volatile solid additive (VSA), 2-hydroxy-4-methoxybenzophenone (2-HM), for achieving high-efficiency ONSCs. 2-HM functions as a universal morphology-directing agent for several well-known PM6:Y6 series nonfullerene blends, viz. PM6:Y6, PM6:BTP-eC9, PM6:L8-BO, leading to a best efficiency of 18.85% at the forefront of reported binary ONSCs. VSAs have recently emerged, while the intrinsic kinetics is still unclear. Herein, we employ a set of in-situ and ex-situ characterizations to first illustrate the molecule-aggregate-domain transition dynamic process assisted by the VSA. More specifically, we unlock the role of 2-HM in individual donor PM6 and acceptor Y6 systems, and further reveal the function of 2-HM in altering the PM6:Y6 bulk heterojunction blends for enhanced photovoltaic performance. We believe the achievement brings not only a deep insight into emerging volatile solid additive, but also a new hope to further improve the molecular ordering, film microstructure and relevant performance of ONSCs. This article is protected by copyright. All rights reserved.