Encapsulation of CsPbBr ₃ quantum dots in silica matrices and study of enhanced nonlinear optical properties

All-inorganic cesium lead halide perovskite quantum dots, CsPbX₃(X = Cl, Br, I), exhibit exceptional potential in nonlinear optical (NLO) applications. This is due to their outstanding optoelectronic properties, including high photoluminescence quantum yield, tunable band gaps, and strong absorption coefficients. However, their practical utility is severely limited by their environmental instability against ambient air and moisture. In this study, CsPbBr₃QDs were encapsulated in a SiO₂matrix using a sol-gel method to fabricate CsPbBr₃/SiO₂gel-glass composites. Structural characterization (transmission electron microscopy, x-ray diffraction, and Fourier transform infrared) confirmed the uniform dispersion and complete encapsulation of the QDs within the amorphous SiO₂network. Optical analyses revealed that the composites retained the intrinsic absorption and emission characteristics of the CsPbBr₃QDs (bandgap: 2.29 eV; fluorescence peak: 510 nm), while exhibiting tunable linear transmittance (50%-82%).<i>Z</i>-scan measurements under 532 nm picosecond pulsed laser excitation revealed significant nonlinear absorption coefficients (<i>β</i>) of up to 0.85 cm GW^-1and a low optical limiting threshold (OL) of 0.22 J cm^-2. Importantly, SiO₂encapsulation markedly enhanced the environmental stability of the CsPbBr₃QDs, and their NLO properties remained stable after 365 d of storage under ambient air conditions. This work provides a viable strategy for realizing halide perovskite-based OL devices and establishes a promising platform for further development. Future device-level integration and cycling tests will be essential for practical deployment.