Heterovalent Samarium Cation‐Doped SnO 2 Electron Transport Layer for High‐Efficiency Planar Perovskite Solar Cells

Tin oxide (SnO 2 ) has demonstrated significant potential as an electron transport layer (ETL) owing to its low‐temperature processing in perovskite solar cells (PSCs). However, the poor energy‐level alignment and the presence of interface defects between the SnO 2 and perovskite layer aggravate the power conversion efficiency (PCE) of the PSCs. Herein, heterovalent samarium cation (Sm 3+ ) is deliberately doped into SnO 2 , optimizing the energy‐level alignment between SnO 2 and the perovskite layer, and effectively passivating the oxygen vacancy defects on the surface of SnO 2 . Experimental and theoretical conclusions reveal that Sm‐doping successfully passivates the defects in the ETL and improves the perovskite crystal quality, thereby reducing interface charge recombination, and enhancing electron extraction from perovskite to the SnO 2 layer. Consequently, the optimized Sm‐doped SnO 2 ‐based PSCs achieve a PCE of 24.10% with a V OC of 1.174 V, negligible hysteresis, and improved durability under ambient conditions.