3D‐Architectured Acceptor with High Photoluminescence Quantum Yield and Moderate Crystallinity for High‐efficiency Organic Solar Cells with Low Voltage Loss

This study outlines a molecular design approach that entails integrating 3D structural motifs into the central core or terminal groups of fused-ring acceptor molecules, specifically, LLZ1, LLZ2, and LLZ3-by incorporating a 3D architecture unit of norbornene. The objective is to modulate the aggregation behavior of these molecules by modifying their molecular structure, thereby enhancing the photoluminescence quantum yield (PLQY) values of the acceptor materials and reducing the non-radiative recombination voltage loss in the corresponding devices. Our research findings demonstrate that the introduction of norbornene units effectively suppresses excessive molecular aggregation and significantly improves the PLQY values of the acceptor molecules. Further research has demonstrated that only the acceptor molecule LLZ1, characterized by both high PLQY and moderate crystallinity, can strike an optimal balance between the dual requirements of reducing voltage loss and enhancing charge transport in the device. Utilizing the preferred molecule LLZ1, we achieved a power conversion efficiency (PCE) of 18.0% in binary system and 20.4% in ternary device with much-reduced voltage loss of 0.508V, which is among the highest values of current OSCs. In summary, this work provides novel insights and research directions for the development of OSCs with low voltage loss and high PCE.