A Novel Substrate‐Free Ultrathin Cyan‐Emitting Phosphor‐Glass Composite Based on Ce‐Activated Ca2YAlGa2Si2O12 Microcrystal

Abstract The substrate‐free ultrathin phosphor‐glass composite (PGC) provides significant advantages for all‐inorganic light‐emitting diodes (LEDs), offering enhanced resistance to light radiation and chemical corrosion. However, achieving a PGC thickness below 100 µm remains challenging due to its brittle nature. Herein, this work presents a novel strategy to fabricate an ultrathin cyan PGC for all‐inorganic LEDs, based on our home‐synthesized Ce‐activated Ca 2 YAlGa 2 Si 2 O 12 phosphor (CYAGS:Ce). The phosphor emits bright cyan light centered at λ em 497 nm with a FWHM of 93 nm and an internal quantum yield (IQY) greater than 60%. The luminescence mechanism, including concentration and thermal quenching, is investigated in detail. Using tape‐casting and low‐temperature co‐firing, an ultrathin PGC with a thickness of 98 µm is achieved. Structural and luminescence properties are compared to highlight the glass matrix's influence. Furthermore, based on as‐prepared ultrathin PGCs, a compact LEDs with a low correlated color temperature (CCT, 3384 K) and high color‐rendering index (CRI, R a = 85.7) is obtained by integrating both red and cyan PGCs with a commercial 420 nm blue chip. This work advances the understanding of CYAGS:Ce cyan phosphor and provides a versatile strategy for fabricating ultrathin PGCs, highlighting their potential applications in all‐inorganic LED lighting.