Laser‐Induced Secondary Crystallization of CsPbBr3 Perovskite Film for Robust and Low Threshold Amplified Spontaneous Emission

Abstract All‐inorganic perovskite nanocrystals (NCs) have received extensive attention for next‐generation thin film devices due to their excellent optical properties, such as strong light absorption, high carrier mobility, and defect tolerance. However, significant challenges remain to obtain high‐quality perovskite thin films. Herein, a simple but effective post‐treatment by laser irradiation for CsPbBr 3 NCs thin films is reported. Laser‐induced secondary crystallization is observed in CsPbBr 3 NCs thin films after treatment. In addition, amplified spontaneous emission (ASE) with a low threshold (5.6 µJ cm −2 ) and a high gain value (743 cm –1 ) is achieved. Based on optical measurements, it is attributed to the low defect density, reduced Auger recombination, and weak exciton–phonon interactions, which greatly suppress the nonradiative recombination channels. The ASE from the film after treatment has a high characteristic temperature (134 K), showing a stable optical gain performance that maintains its intensity for 35 h at room temperature (and 12 h at 40 °C). Finally, the proof‐of‐concept demonstration of graphic coding is shown. This study deepens the understanding of the optical gain mechanism of CsPbBr 3 perovskite films and provides a simple and convenient laser treatment that enables the fabrication of high‐quality CsPbBr 3 perovskite thin films.