Coagulated SnO₂ Colloids for High‐Performance Planar Perovskite Solar Cells with Negligible Hysteresis and Improved Stability

Organic–inorganic perovskite solar cells with a planar architecture have attracted much attention due to the simple structure and easy fabrication. However, the power conversion efficiency and hysteresis behavior need to be improved for planar‐type devices where the electron transport layer is vital. SnO 2 is a promising alternative for TiO 2 as the electron transport layer owing to the high charge mobility and chemical stability, but the hysteresis issue can still remain despite the use of SnO 2 . Now, a facile and effective method is presented to simultaneously tune the electronic property of SnO 2 and passivate the defects at the interface between the perovskite and SnO 2 . The perovskite solar cells with ammonium chloride induced coagulated SnO 2 colloids exhibit a power conversion efficiency of 21.38 % with negligible hysteresis, compared to 18.71 % with obvious hysteresis for the reference device. The device stability can also be significantly improved.