Enhanced Thermal Durability and Efficiency of Organic Solar Cells via Selective Organic Electron Transport Layers

Abstract

For commercialization of organic solar cells, achieving high power conversion efficiency and prolonged thermal stability remains critical. We systematically investigated the thermal durability of PM6:Y6-based organic solar cells incorporating PDINN and PFN-Br as organic electron transport layers. PDINN-based organic solar cells achieved an exceptional power conversion efficiency of 17.06% at room temperature and remarkably maintained >15% power conversion efficiency even under harsh 110 degrees C thermal treatment. In contrast, PFN-Br-based devices initially showed 15.26% power conversion efficiency but exhibited significantly reduced performance with increasing processing temperatures. To elucidate the contrasting thermal behaviors, we conducted a comprehensive comparative analysis of both organic electron transport layer films and their effects on the PM6:Y6 active layer through advanced thermal analysis, optical spectroscopy, surface morphological characterization, and detailed charge dynamics investigations. Our findings reveal that PDINN-based devices demonstrated superior charge transport efficiency and effectively suppressed recombination processes under thermal stress, primarily attributed to strong hydrogen bonding interactions between PDINN's amine groups and Y6 acceptor molecules. Conversely, PFN-Br-based organic solar cells exhibited poor thermal durability due to detrimental bromide ion migration and accumulation at the silver electrode interface. This study demonstrates the critical importance of strategic interfacial engineering for simultaneously improving both efficiency and thermal stability of organic solar cells, providing insights for next-generation thermally resistant organic photovoltaics.