Record‐Efficiency Inverted CsPbI3 Perovskite Solar Cells Enabled by Rearrangement and Hydrophilic Modification of SAMs

Abstract Recently, the inverted CsPbI 3 perovskite solar cells (PSCs) have attracted extensive attentions due to their potential to combine with silicon solar cells for tandem devices with theoretical power conversion efficiency (PCE) of 44%. However, the reported self‐assembled molecules (SAMs) as hole selected layer for inverted PSCs have poor wettability and serious agglomeration, which greatly limits the efficiency and stability of PSCs. To address above problem, niobium pentachloride (NCL) is applied to prevent SAMs agglomeration for a homogenous SAMs film with a hydrophilic surface. The optimized SAMs surface facilitates the deposition of the cesium lead triiodide (CsPbI 3 )film with an enhanced referred orientation, suppressed defects, and released stress. Consequently, the NCL‐treated CsPbI 3 PSCs achieved a champion PCE of 21.24%, which is the highest PCE value for inverted all‐inorganic PSCs. The optimized device maintained 97.61% initial PCE after 1000 h storage in air, and 92.27% initial PCE after 1000 h tracking at the maximum power point (MPP).