Preparation and Fluorescence Properties of Silicon-Coated Cruciform CsPbBr₃ Nanocrystals

All-inorganic perovskite nanocrystals (NCs) offer excellent optoelectronic properties but suffer from poor stability under environmental factors such as water, oxygen, and heat, which limits their broader applications. To address this, we developed a two-stage heating method to synthesize cruciform CsPbBr₃ NCs, followed by embedding them in a silica matrix to enhance both fluorescence and stability. The CsPbBr₃ NCs measured 30.5 nm in length and 28.5 nm in width. Coating with SiO₂, derived from 3-aminopropyl triethoxysilane (APTES) with an APTES/Pb molar ratio of 2.0, increased the photoluminescent quantum yield (PLQY) from 65% to 87%. The CsPbBr₃@SiO₂ composite retained 27% of its fluorescence after 210 min in ethanol, while the pristine CsPbBr₃ NCs were almost fully quenched. After storage in water for 24 h, the PL intensity was 43.5% for the CsPbBr₃@SiO₂ composite and 3.6% for uncoated NCs. At 398 K, the composite retained 31% of its PL while uncoated NCs were nearly fully quenched. The CsPbBr₃@SiO₂-based white-light-emitting diode (WLED) exhibited a color rendering index (CRI) of 40.4, a correlated color temperature (CCT) of 5218 K, and a luminous efficiency of 35 lm/W, covering 134.5% of the NTSC color gamut, demonstrating excellent potential in WLED applications.