Light‐Soaking Induced Optical Tuning in Rare Earth‐Doped All‐Inorganic Perovskite

Abstract Understanding and manipulating the photoluminescence (PL) of all‐inorganic perovskites is significant in applications toward light‐emitting diodes. Doping has proved to be a very promising approach for tuning the luminescence properties of perovskites. Herein, rare earth (Er and Yb) doped 3D all‐inorganic perovskite flakes (CsPb(Cl/Br) 3 ) are synthesized. At room temperature, they possess a narrow emission peak at 506 nm with 10 nm linewidth and a quite broad peak at 700 nm with 170 nm linewidth, which are from band‐edge PL of α‐CsPb(Cl/Br) 3 and self‐trapped excitons of δ‐CsPb(Cl/Br) 3 , respectively. When exposing the flakes under a light‐soaking, the samples present a color tuning capability spanning from red to green by extension of the soaking time, and the emission properties can recover by removing the light‐soaking and undergoing a certain recovery time. Time‐resolved photoluminescence indicates a photoinduced reduction of defects density in the doped perovskite flakes. Based on further density functional theory calculations, a photoinduced O 2 ‐diffused defect‐passivation mechanism is proposed. The discovery is expected to promote the optical tuning capability of the all‐inorganic perovskites and expand their potential application in optoelectronics devices.