Waterproof Cesium Lead Bromide Perovskite Lasers and Their Applications in Solution

The many advantageous optoelectronic properties of lead halide perovskites have made them promising materials in both solar cells and light source applications. However, lead halide perovskites are soluble in polar solvents, which hinders their practical applications. Thus, the effective protection of perovskite against polar solvents is of great significance. Herein, we report a waterproof CsPbBr₃ nanoplate (NP) laser protected by large-scale on-chip microprocess-compatible atomic layer deposition (ALD) Al₂O₃. The 50 nm Al₂O₃ coated CsPbBr₃ NPs can continuously lase in water for over an hour and can still lase after being immersed in water for a month. Moreover, the lasing behaviors of the 20 nm Al₂O₃ coated CsPbBr₃ NP, in the mixed solution of water and glycerine with the refractive index ranging from 1.33 to 1.47, are also studied. As the environmental refractive index increases, the NP laser goes through a mode selection process, showing single-mode (540.3 nm) to dual-mode and to single-mode (533.9 nm) lasing behavior, which is caused by mode competition resulting from the decrease of quality factor (Q factor) and the blue-shift of the material's gain spectra. Besides, lasing thresholds of the CsPbBr₃ NP increase with the environmental refractive index, which can be utilized for sensing with a measured sensitivity of 129.7 μJ cm^-2 RIU^-1 (per refractive index unit) (388.2 μJ cm^-2 RIU^-1) for the long (short)-wavelength lasing mode. Our work demonstrates that the ALD Al₂O₃ protection method can effectively protect CsPbBr₃ against polar solvents, enhance the material's stability, and enable perovskite's practical applications in both on-chip integration and solvent systems.