Environmentally stable Mn-doped CsPbX3@CsPb2X5 core–shell materials with efficient energy transfer†

Abstract

Mn(II)-doped cesium lead halide perovskite (CsPbX₃ (X = Cl, Br, I)) quantum dots (QDs) have attracted a lot of attention from researchers attributed to their bright orange light emission. However, defects such as inefficient energy transfer and instability have hindered the commercial application of the material. Here, we propose a convenient core–shell coating strategy to epitaxially grow a CsPb₂X₅ shell on Mn-doped CsPbX₃ surfaces by controlling the reaction time and precursor ratio. Meanwhile, density-functional theory (DFT) calculations indicate that a typical type-I heterojunction is formed between the CsPb(Cl/Br)₃ cores and the CsPb₂(Cl/Br)₅ shell, which improves the energy transfer efficiency from an exciton to Mn²⁺. The obtained Mn-doped CsPb(Cl/Br)₃@CsPb₂(Cl/Br)₅ core–shell materials exhibit enhanced optical properties and excellent water/thermal stability. Subsequently, the white light-emitting diode prepared from the composites shows a high luminescence efficiency of 127.21 lm W⁻¹, and the PL intensity is still maintained above 95% after 24 h of continuous operation.