Dual Functions of Halogen-Bonding Molecules for Stabilizing Ultra-wide Bandgap Perovskite Solar Cells

Ultra-wide-bandgap (UWBG) metal halide perovskite solar cells are essential for multi-junction solar cells with higher power conversion efficiency (PCE) potentials. In this work, we report the dual functions of 5-iodoisophthalic acid (I-BDC) to suppress phase segregation and uncoordinated Pb2+ related defects to enhance UWBG perovskite cell performance and stability. An I-BDC incorporated 1.95 eV perovskite film exhibited stable photoluminescence after 120 min of illumination. The best I-BDC cell achieved a certified reverse scan PCE of 16.5%, the highest for 1.95 eV perovskite cells to date. These UWBG perovskite solar cells are the most stable reported to date, with one encapsulated device retaining 90% of its initial PCE after 500 h of maximum power point tracking at ∼40 °C and another retaining 95% of its initial PCE after 206 thermal cycles (–40 ↔ 85 °C), passing the International Electrotechnical Commission (IEC) 61215 testing protocols at the cell level.