Efficient Organic Solar Cells with 19.5% Power Conversion Efficiency Achieved via a Deuterium-Substituted Y6

Rapid advances in organic solar cells (OSCs) have attracted significant attention in recent years, especially after the emergence of Y6 and its derivatives. Despite the remarkable progress that has been successfully achieved, challenges such as low power conversion efficiency (PCE) and unsatisfactory stability remain. While there is considerable potential in the application of deuterated small-molecule electron acceptors to address these two issues, there is also a lack of consensus in the research outcomes, which suggests that further investigation is required. To further investigate deuterium-substituted small-molecule electron acceptors, the dideuterated analogue of Y6 (Y6-d2) was synthesized with the aim of simultaneously enhancing the PCE and stability of OSCs. Y6-d2 exhibits a more compact crystal structure while maintaining the same energy levels and absorption characteristics as those of Y6. This gives rise to larger phase separation in the blend film with PM6 and enhances the resultant photovoltaic performance of the device. While exhibiting comparable open-circuit voltage (VOC, 0.843 V), the PM6:Y6-d2-based device demonstrates superior performance with an intensively improved short-circuit current density (JSC, 28.48 mA cm–2) and fill factor (FF, 81.3%). These improvements, in turn, significantly boost the device’s PCE up to 19.5% and long-term stability of its initial efficiency over 96% after 1200 h storage, surpassing the 18.86% and 84% of the benchmark PM6:Y6 device, confirming the effectiveness of dieuterated Y6 for enhancing PCE and improving stability for OSCs.