Thermally Stable Copper(II)-Doped Cesium Lead Halide Perovskite Quantum Dots with Strong Blue Emission

All-inorganic perovskite quantum dots (QDs) have emerged as potentially promising materials for lighting and displays, but their poor thermal stability restricts their practical application. In addition, optical characteristics of the blue-emitting CsPbX₃ QDs lag behind their red- and green-emitting counterparts. Herein, we addressed these two issues by doping divalent Cu²⁺ ions into the perovskite lattice to form CsPb_{1- x}Cu _xX₃ QDs. Extended X-ray absorption fine structure (EXAFS) measurements reveal that doping smaller Cu²⁺ guest ions induces a lattice contraction and eliminates halide vacancies, which leads to an increased lattice formation energy and improved short-range order of the doped perovskite QDs. This results in the improvement of both the thermal stability and the optical performance of CsPb_{1- x}Cu _x(Br/Cl)₃ QDs, which exhibit bright blue photoluminescence at 450-460 nm, with a high quantum yield of over 80%. The CsPb_{1- x}Cu _xX₃ QD films maintain stable luminescence performance even when annealed at temperatures of over 250 °C.