In recent years, there has been rapid progress in the development of photonic devices based on lead halide perovskite nanocrystals since they possess a set of unique optical and charge transport properties. However, the main limiting factor for their subsequent application is poor stability against exposure to adverse environmental conditions. In this work, a study of a composite material based on perovskite CsPbBr₃ nanocrystals embedded in porous silica microspheres is presented. We developed two different approaches to change the interface between nanocrystals and the surface of the microsphere pores: surface treatment of (i) nanocrystals or (ii) microspheres. The surface modification with tetraethylorthosilicate molecules not only increased stability but also improved the optical responses of the composite material. The position of the emission band remained almost unchanged, but its lifetime increased significantly compared to the initial value. The improvement of the optical performance via surface modification with tetraethylorthosilicate molecules also works for the lead-free Bi-doped Cs₂AgInCl₆ double perovskite nanocrystals leading to increased stability of their optical responses at ambient conditions. These results clearly demonstrate the advantage of a composite material that can be used in novel photonic devices with improved performance.