Sequential passivation strategy enables ultra‑stable CsPbX3 perovskite quantum dots for high‑color‑rendering white light‑emitting diodes

All-inorganic cesium lead halide perovskite quantum dots (CsPbX 3 QDs) exhibit exceptional optoelectronic properties but suffer from poor stability under ambient conditions, which severely limits their practical applications. In this work, a sequential passivation strategy was developed to simultaneously enhance the photoluminescence quantum yields (PLQYs) and long-term stability of CsPbX 3 QDs. First, 4-bromobutyric acid (BBA) and oleylamine (OLA) were employed as co-ligands during a recrystallization synthesis in aqueous solution, yielding BBA/OLA-capped CsPbX 3 QDs with improved water resistance. Subsequently, the as-prepared QDs were further treated with phenethylammonium bromide (PEABr) to passivate residual surface defects, particularly bromide vacancies, forming a dense hydrophobic ligand shell. Systematic characterization using transmission electron microscopy, X-ray diffraction, UV–vis absorption, photoluminescence spectroscopy, and X-ray photoelectron spectroscopy revealed that the sequential passivation not only refines the morphology and crystallinity but also significantly suppresses non-radiative recombination. The resulting PEABr/BBA/OLA-CsPbX 3 QDs exhibit superior stability under various harsh conditions, including high humidity (70% RH), water immersion, continuous UV irradiation (365 nm), and elevated temperatures (up to 100 °C). As a proof of concept, a white light-emitting diode (WLED) was fabricated using the passivated QDs as the green-emitting layer together with a commercial InGaN blue chip and CsPb(Br/I) 3 red QDs. The device achieves Commission Internationale de l’Éclairage (CIE) color coordinates of (0.3302, 0.3261), a correlated color temperature of 5650 K, and a high color rendering index of 96, demonstrating stable white emission under varying driving currents. This sequential passivation strategy provides a facile and effective route to high-performance, ultra-stable CsPbX 3 QDs for next-generation display and solid-state lighting applications.