In Situ Synthesis of UltraStable TiO2 Coating Rb+-Doped Red Emitting CsPbBrI2 Perovskite Quantum Dots

Among the lead halide perovskites, the stability of red-emitting CsPbBrI2 perovskite quantum dots (PQDs) is very poor. This is an impediment to the development of high purity white emitting diodes (WLEDs) based on PQDs. Herein, we surprisingly find that luminescent properties of CsPbBrI2 PQDs can be significantly improved through doping of univalent Rb+ ions, especially when molar ratio of Rb+/Cs+ = 0.1/0.9. Subsequently, these red emitting Rb0.1Cs0.9PbBrI2 PQDs are successfully coated with TiO2 through an easy in situ strategy of adding titanium(IV) butoxide (TBO) to the precursor. Benefiting from the efficient protection of TiO2 nanoshell, these highly fluorescent Rb0.1Cs0.9PbBrI2/TiO2 nanocomposites can preserve their excellent red emitting characteristics even when directly immersed in water or exposed to illumination, enabling us to build highly stable WLEDs with color coordinates at (0.342, 0.325).