Water-Stable Perovskite Quantum Dots for Wide-Color-Gamut White-Light-Emitting Diodes

Perovskite quantum dots (PQDs) based on CsPbX3 (X = Cl, Br, I) have attracted extensive attention due to their outstanding optoelectronic properties; however, their practical applications are hindered by poor environmental stability. In this work, a sequential surface-modification strategy is developed to address these limitations. First, CsPbBr3 PQDs are passivated with (3-aminopropyl) triethoxysilane (APTES), which reduces surface defects and enhances the photoluminescence quantum yield (PLQY) from 38.5% to 74.4%. Subsequently, a dense silica shell is constructed via in situ hydrolysis of tetramethyl orthosilicate (TMOS), further improving the PLQY to 95.6% and significantly boosting environmental stability. Structural and optical characterizations confirm effective defect passivation and suppress non-radiative recombination, with carrier lifetimes extended from 2.5 ns to 36.9 ns. Remarkably, the silica-coated PQDs retain over 50% of their initial emission intensity after 100 min of water immersion, far exceeding the stability of uncoated counterparts. Furthermore, when integrated with a commercial K2SiF6: Mn4+ red phosphor and a blue light-emitting diode (LED) chip, the resulting white LED (WLED) exhibits a wide color gamut covering 104% of the National Television System Committee (NTSC) standard and Commission Internationale de l’Éclairage (CIE) coordinates of (0.323, 0.331), closely matching standard white light. Importantly, only the silica-coated PQDs maintain a stable electrically driven device emission spectrum after water exposure.