Ultrastable and Reversible Fluorescent Perovskite Films Used for Flexible Instantaneous Display

Abstract All‐inorganic halide perovskite materials are regarded as promising materials in information display applications owing to their tunable color, narrow emission peak, and easy processability. However, the photoluminescence (PL) stability of halide perovskite films is still inferior due to their poor thermal stability and hygroscopic properties. Herein, all‐inorganic perovskite films are prepared through vacuum thermal deposition method to enhance thermal and hygroscopic stability. By intentionally adding extra bromide source, a structure of CsPbBr 3 nanocrystals embedded in a CsPb 2 Br 5 matrix (CsPbBr 3 /CsPb 2 Br 5 ) is formed via an air exposure process, leading to impressive PL stability in ambient atmosphere. In addition, the as‐fabricated CsPbBr 3 /CsPb 2 Br 5 structure shows enhanced PL intensity due to the dielectric confinement. The CsPbBr 3 /CsPb 2 Br 5 structure film can almost reserve its initial PL intensity after four months, even stored in ambient atmosphere. The PL intensity for CsPbBr 3 /CsPb 2 Br 5 films vanishes at elevated temperature and recovers by cooling down in a short time. The reversible PL conversion process can be repeated over hundreds of times. Based on the reversible PL property, prototype thermal‐driven information display devices are demonstrated by employing heating circuits on flexible transparent substrates. These robust perovskite films with reversible PL characteristics promise an alternative solid‐state emitting display.