Deuterated Solvents Yield Organic Solar Cells with Enhanced Efficiency and Thermal Stability

The utilization of deuterium plays a crucial role in advancing the fundamental understanding of aggregate materials and their emerging functionalities. Specifically, resolving the solution structure of conjugated polymers becomes challenging in the absence of deuteration, particularly when employing solvents with high X-ray absorption coefficients such as chloroform. Nevertheless, there is a dearth of studies investigating the isotopic effects of casting solvents on the aggregated structures of photovoltaic polymers and their bulk-heterojunction blends. In this study, we presented a feasible and widely applicable approach of using deuterated organic solvents to establish the structure-performance relationships of organic solar cells (OSCs). We also unraveled the isotope effect of casting solvents on photovoltaic polymer systems from the aspects of thermal properties, molecular stacking, morphology, and device performance. This is the first-ever report to showcase the potential of deuterated solvent in OSCs. Our findings highlight the pronounced impact of relatively poor miscibility between deuterated solvents and photovoltaic polymers, which leads to an enhanced π-π stacking order. Furthermore, the utilization of deuterated solvents in film processing facilitates higher crystallinity and optimized morphology, resulting in improved device efficiency and notable enhancement in thermal stability. These results underscore the significance of solvent isotopic effects on the aggregated structure of conjugated polymer systems and unveil the potential of innovative approaches for fabricating high-efficiency solar cells with enhanced thermal stability.