Stable CsPbBr₃:Sn@SiO₂ and Cs₄PbBr₆:Sn@SiO₂ Core–Shell Quantum Dots with Tunable Color Emission for Light-Emitting Diodes

CsPbBr3 perovskite quantum dots (QDs) have attracted great attention due to their different photoluminescent and electronic properties. However, the toxicity and low stability hinder their practical application. Here, low-toxicity Sn-substituted cesium lead bromide perovskite QDs were synthesized via the room temperature crystallization method. A phase transition of the perovskite quantum dots with the concentration of Sn increasing was found: the crystal phase of CsPbBr3:Sn perovskite QDs starts to be transformed into Cs4PbBr6:Sn perovskite QDs when the SnBr2 precursor exceeds 30 at. %. In this process, the controlled-color emission of perovskite QDs from green to blue can be realized. To improve the stability of quantum dots, CsPbBr3:Sn@SiO2 and Cs4PbBr6:Sn@SiO2 were synthesized via a simple one-step synthesis with hydrolysis of tetramethoxysilane in toluene solution containing perovskite QDs. The results show that CsPbBr3:Sn@SiO2 and Cs4PbBr6:Sn@SiO2 exhibited higher water stability and water solubility than pure QDs. In a mixed solution of toluene and water, the PL intensity of the CsPbBr3:Sn@SiO2 retained 46.7% and the Cs4PbBr6:Sn@SiO2 was 59.6% even after 24 h of reaction compared with the initial intensities. These quantum dots with good stability and luminescent property developed in this work are expected to be widely used in light-emitting diodes.