Enhancing Interfacial Contact for Efficient and Stable Inverted Perovskite Solar Cells and Modules

Abstract Defective perovskite surfaces severely limit the development of inverted perovskite solar cells (PSCs). Here, the impacts of surface treatment are systematically investigated with organic ammonium salts, namely piperidinium iodide (PpI) and piperazinedihydroiodide (PDI), on the performance of the formamidinium‐cesium (FACs)‐based PSCs. These results indicate that PpI, with its high dipole moment, tends to form 1D structures on the perovskite surface, which hinders electron transport. By contrast, PDI post‐treatment does not lead to the formation of such structures; instead, it forms a thin passivation layer that homogenizes the electric potential across the perovskite surface. This merit results in a favorable alignment of energy levels and a significant reduction in non‐radiative recombination at the perovskite/electron transport layer interface. As a result, the inverted perovskite solar module (PSM) achieved a power conversion efficiency (PCE) of 22.08% with an aperture area of 11.1 cm 2 (certified 21.58%), showing a low‐efficiency discrepancy versus the small‐area counterpart with an efficiency of 25.09%. Notably, the PSM can maintain 92.5% of its initial PCE after continuous 1000 h of 1‐sun operation at 65 °C in ambient air.