Epitaxial Growth of CsPbX3 (X = Cl, Br, I) Perovskite Quantum Dots via Surface Chemical Conversion of Cs2GeF6 Double Perovskites: A Novel Strategy for the Formation of Leadless Hybrid Perovskite Phosphors with Enhanced Stability

Lead halide perovskites (LHPs) have received increased attention owing to their intriguing optoelectronic and photonic properties. However, the toxicity of lead and the lack of long-term stability are potential obstacles for the application of LHPs. Herein, the epitaxial synthesis of CsPbX3 (X = Cl, Br, I) perovskite quantum dots (QDs) by surface chemical conversion of Cs2GeF6 double perovskites with PbX2 (X = Cl, Br, I) is reported. The experimental results show that the surface of the Cs2GeF6 double perovskites is partially converted into CsPbX3 perovskite QDs and forms a CsPbX3/Cs2GeF6 hybrid structure. The theoretical calculations reveal that the CsPbBr3 conversion proceeds at the Cs2GeF6 edge through sequential growth of multiple PbBr64- layers. Through the conversion strategy, luminescent and color-tunable CsPbX3 QDs can be obtained, and these products present high stability against decomposition due to anchoring effects. Moreover, by partially converting red emissive Cs2GeF6:Mn4+ to green emissive CsPbBr3, the CsPbBr3/Cs2GeF6:Mn4+ hybrid can be employed as a low-lead hybrid perovskite phosphor on blue LED chips to produce white light. The leadless CsPbX3/Cs2GeF6 hybrid structure with stable photoluminescence opens new paths for the rational design of efficient emission phosphors and may stimulate the design of other functional CsPbX3/Cs-containing hybrid structures.