Lead–halide perovskite nanocrystals (PeNCs), especially those composed of iodine, suffer from degradation problems. Water vapor, oxygen, light, and heat can damage PeNCs and consequently quench their photoluminescence (PL). Thus, robust encapsulation against all these stresses is urgently required. In this study, inorganic encapsulation of mesoporous SiO₂, in conjunction with a high-temperature sintering synthesis process under an inert atmosphere, is introduced. This synthesis process is compatible with various halide contents, yielding PeNCs sealed in SiO₂ particles that emit PL emission covering the entire visible range from 420 to 700 nm. The PeNCs–SiO₂ sample showed remarkable stability after undergoing aging tests under various exaggerated stresses as well as mitigated thermal quenching during thermal cycling. The color gamut constituted by three PeNCs–SiO₂ samples approached 135.36% NTSC and 101.07% Rec. 2020, with remarkable chromatic stability. The PeNCs–SiO₂ can be blended into a photoresist and remains luminous during the development procedure, which is compatible with the photolithography process; this facilitates the mass production of color conversion layers. All these advantageous features show that the material proposed herein has great potential for application in full-color displays such as micro and mini light-emitting diode displays.