In this work, CsPbBr3/Cs4PbBr6@glass composites were synthesized by incorporating lead carbonate (PbCO3) into a lithium-aluminum-silicate-boron (Li-Al-Si-B) glass matrix. PbCO3 decomposes to PbO, which reacts in situ with melt Br to form PbBr2, triggering CsPbBr3/Cs4PbBr6 nucleation in Br-rich microdomains; CO2 release concurrently creates stress-relieving micropores, outperforming direct PbBr2 addition. This composite exhibited remarkable photoluminescence properties, with a photoluminescence quantum yield (PLQY) reaching as high as 86.71%. In an accelerated aging experiment conducted over 120 h, the fluorescence intensity was maintained at 95% of its original value. Even after 60 days of immersion in water, the luminescence intensity remained at 94% of the initial intensity, demonstrating its outstanding resistance to environmental degradation. To further explore its potential for display applications, we prepared a CsPbBr3/Cs4PbBr6/CsPbBrI2@glass@polystyrene (PS) film. This film exhibited an impressive color gamut, covering 123% of the National Television System Committee (NTSC) 1953 standard and 91.3% of the ITU-R Recommendation BT.2020 (Rec.2020) standard. The high PLQY and excellent stability of CsPbBr3/Cs4PbBr6@glass make it highly suitable for LCD applications and offer broad prospects for industrial-scale production.