Selective Chemical Etching to Remove 0D Cs 4 Pb(IBr) 6 from Mixed‐Dimensional Perovskite Surface Achieving High Efficiency Flexible All‐Inorganic Perovskite Solar Cells with Superior Mechanical Durability

All‐inorganic cesium lead halide flexible perovskite solar cells (f‐PSCs) exhibit superior thermal stability compared to their organic‐inorganic hybrid counterparts. However, their flexibility and efficiency are still below‐par for practical viability. This study presents an approach involving the introduction of multifunctional molecule ammonium benzenesulfonate (ABS) to selectively etch 0D‐Cs 4 Pb(IBr) 6 from the mixed‐dimensional perovskite film surface, to attain more contact area between the perovskite and hole transport layer for improved hole extraction and transport. It is found that the ABS molecules bind to the perovskite lattice surface via O atoms and NH 4 + , effectively passivating surface defects and enhancing phase stability. The hydrophobic nature of the benzene ring in ABS further contributes to operational stability, leading to high cell efficiency of 15.00%, accompanied by enhanced operational stability. Even after undergoing 60 000 flexing cycles at a curvature radius of 5 mm, the ABS‐treated f‐PSC still retains over 98.5% of its initial efficiency. This multifunctional strategy for modifying typical mixed‐dimensional perovskite compositions significantly enhances the photovoltaic performance and stability of flexible all‐inorganic f‐PSCs.