Comprehensive Defect Suppression in Te‐Doped Cs₂ZrCl₆ Perovskite Nanoparticles for Highly Efficient and Thermally Stable White Light‐Emitting Diodes

Abstract Cesium zirconium halide (e.g., Cs2ZrCl6:Te or CZCT) perovskites have garnered significant interest due to their unique optical properties. However, there have been no reports of CZCT perovskite nanoparticles (PNPs) that simultaneously offer high efficiency and thermal stability. Here, a comprehensive defect suppression strategy is reported to achieve CZCT PNPs with these attributes. First, the inner defects of CZCT perovskite microcrystals (PMCs) are minimized by controlling crystallization kinetics precisely. Second, the PNPs are obtained from PMCs via top‐down fabrication, and the surface defects of PNPs are passivated via the hydroxyl groups of alkyl‐terminated silica‐oligomer shell (ASO). The resulting CZCT@ASO PNPs show the highest photoluminescence quantum yield (PLQY) of 96% and high thermal stability among the reported conventional CZCT emitters. Finally, white light‐emitting diodes (WLEDs) are integrated by using CZCT@ASO PNPs as the down‐color converters, achieving a color coordinate of (0.31, 0.33) and a color rendering index of 86. These results demonstrate that core/shell CZCT@ASO PNPs have great potential as phosphors for lighting applications.