Highly Luminescent Lead Halide Perovskite Quantum Dots in Hierarchical CaF2 Matrices with Enhanced Stability as Phosphors for White Light‐Emitting Diodes

Abstract Lead halide perovskite quantum dots (PQDs) have been widely recognized as highly luminescent materials for efficient optoelectronic applications owing to their fascinating electronic and optical properties. In spite of the excellent performances for the fabrication of lighting devices, the poor chemical instability greatly hampers their practical applications. The inevitable ion exchange and degradation driven from light, moisture, heat, and others limits their applications such as solid‐state light‐emitting diodes (LEDs). In this paper, the stability of PQDs is improved by integrating them in CaF 2 hierarchical nanospheres (HNSs). In comparison with the pristine perovskite materials, the outstanding optical performances are well preserved. The perovskite displays a unique quantum confinement effect in the HNSs. Additionally, embedding the quantum dots in robust CaF 2 matrices protects them from being damaged by moisture or light irradiation as well as anion exchange. Furthermore, white LED devices are obtained by mixing green CaF 2 ‐CsPbBr 3 composites and commercial red phosphors on a blue chip. The optimized devices show a high luminous efficacy of 62.7 lm W –1 under 20 mA current and preserve the value of 56.3 lm W –1 after working for 8 h.