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 CsPbBr3 NCs thin films is reported. Laser‐induced secondary crystallization is observed in CsPbBr3 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 CsPbBr3 perovskite films and provides a simple and convenient laser treatment that enables the fabrication of high‐quality CsPbBr3 perovskite thin films.

Self-powered photodetectors based on nanomaterials have attracted lots of attention for several years due to their various advantages. In this paper, we report a high performance Cu2O/ZnO self-powered photodetector fabricated by using electrochemical deposition. ZnO nanowires arrays grown on indium-tin-oxide glass are immersed in Cu2O film to construct type-II band structure. The Cu2O/ZnO photodetector exhibits a responsivity of 0.288 mA/W at 596 nm without bias. Compared with Cu2O photoconductive detector, the responsivity of the Cu2O/ZnO self-powered photodetector is enhanced by about two times at 2 V bias. It is attributed to the high power conversion efficiency and the efficient separation of the photogenerated electron–hole pairs, which are provided by the heterojunction. The outstanding comprehensive performances make the Cu2O film/ZnO nanowires self-powered photodetector have great potential applications.

Four GaAs/Ga(As)Sb/GaAs SQW NWs with different morphologies and photon energies from 1.323 eV to 0.762 eV were achieved.