Interfacial Engineering for Efficient Low‐Temperature Flexible Perovskite Solar Cells

Abstract Photovoltaic technology with low weight, high specific power in cold environments, and compatibility with flexible fabrication is highly desired for near‐space vehicles and polar region applications. Herein, we demonstrate efficient low‐temperature flexible perovskite solar cells by improving the interfacial contact between electron‐transport layer (ETL) and perovskite layer. We find that the adsorbed oxygen active sites and oxygen vacancies of flexible tin oxide (SnO 2 ) ETL layer can be effectively decreased by incorporating a trace amount of titanium tetrachloride (TiCl 4 ). The effective defects elimination at the interfacial increases the electron mobility of flexible SnO 2 layer, regulates band alignment at the perovskite/SnO 2 interface, induces larger perovskite crystal growth, and improves charge collection efficiency in a complete solar cell. Correspondingly, the improved interfacial contact transforms into high‐performance solar cells under one‐sun illumination (AM 1.5G) with efficiencies up to 23.7 % at 218 K, which might open up a new era of application of this emerging flexible photovoltaic technology to low‐temperature environments such as near‐space and polar regions.