Highly efficient and stable red perovskite quantum dots through encapsulation and sensitization of porous CaF ₂ :Ce,Tb nanoarchitectures

Lead halide perovskite quantum dots (PQDs) are extremely unstable when exposed to oxygen, water and heat, especially red CsPbBr_xI_3-x (x = 0, 0.5, 1.2) PQDs. This seriously hinders their practical application. Here, red CsPbBr_xI_3-x (x = 0, 0.5, 1.2) PQDs have been successfully encapsulated in porous CaF₂:Ce,Tb hierarchical nanospheres (HNSs), which not only greatly improved the stability of PQDs, benefitting from the protection of the CaF₂ shell, but also maintained the high photoluminescence quantum yield (PLQY) of PQDs, benefitting from the sensitization of Tb³⁺ ions. More importantly, porous CaF₂:Ce,Tb nanoarchitectures can prevent aggregation quenching and anion exchange of PQDs. Therefore, the CaF₂:Ce,Tb&CsPbBr_xI_3-x (x = 0, 0.5, 1.2) composite powder can have high PLQY comparable to that of the PQD powder. In view of this, CaF₂:Ce,Tb&CsPbBr_1.2I_1.8 composite based red light-emitting diodes (LEDs) are prepared, and they are very suitable as a supplementary light source for plant lighting. Furthermore, white LEDs are also prepared by coating the CaF₂:Ce,Tb&CsPbBr₃ and CaF₂:Ce,Tb&CsPbBr_1.2I_1.8 composite on a 450 nm chip. The optimum luminous efficiency is 61.2 lm W^-1, and the color rendering index is 91, which are comparable to the current highest values. This shows that the composite composed of PQDs has great potential in LED lighting.