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 CaF2 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 CaF2 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 CaF2‐CsPbBr3 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.

Highly Efficient and Water‐Stable Lead Halide Perovskite Quantum Dots Using Superhydrophobic Aerogel Inorganic Matrix for White Light‐Emitting Diodes

“…[20,22,24] Herein, we adopted the widely used green PQDs to investigate their reliability against moisture. [20,22,24] Herein, we adopted the widely used green PQDs to investigate their reliability against moisture.…”

“…PL decay fitting parameters: fast decay time t 1 , slow decay time t 2 , t 1 proportion a 1 , t 2 proportion a 2 , and average decay time t avg , and PLQY of different PQD samples corresponding to Figure 4a-e; particularly, the PL decay curves of the AeroPQDs were fitted using monoexponential function. [16][17][18][19][20]26] Please note that in some previous studies, the reliability of PQDs was evaluated by placing them on water instead of soaking them. Accordingly, the mass ratio of 5:1 was selected for all subsequent tests.…”

“…[4] Particularly, PQDs suffer from low chemical and optical stabilities, resulting in their fast degradation under exposure to moisture, heat, and light irradiance. [13,14] Current research efforts therefore aim at enhancing the stability of PQDs by covering them in inorganic materials, including CdS, [15] zeolite, [16,17] glass, [18,19] CaF 2 , [20] Al 2 O 3 , [21][22][23] SiO 2 , [24][25][26][27][28][29] and TiO 2 . [13,14] Current research efforts therefore aim at enhancing the stability of PQDs by covering them in inorganic materials, including CdS, [15] zeolite, [16,17] glass, [18,19] CaF 2 , [20] Al 2 O 3 , [21][22][23] SiO 2 , [24][25][26][27][28][29] and TiO 2 .…”

“…[30] Generally, the protective shells of PQDs are prepared using these inorganic materials by in situ synthesis. For instance, the PL intensity of CaF 2 shell-integrated green PQDs reduces to <50% after a water-resistance test of ≈40 h. [20] Consequently, and until now, PQDs with high water stability are achieved by embedding them in enclosed organic polymer and glass matrices. For instance, the PL intensity of CaF 2 shell-integrated green PQDs reduces to <50% after a water-resistance test of ≈40 h. [20] Consequently, and until now, PQDs with high water stability are achieved by embedding them in enclosed organic polymer and glass matrices.…”

Highly Efficient and Stable Inorganic Perovskite Quantum Dots by Embedding into a Polymer Matrix

“…For instance, the perovskite QDs have poor stability and suffer from hydrolysis in polar solvents, even from atmospheric condition, which becomes a major issue to their biological and optoelectronic applications ,. Moreover, the fast anion‐exchange reaction between different halide perovskite QD particles results in different emission wavelengths to be incompatible, which limits the application in lighting ,,…”