Stabilizing Cesium Lead Halide Perovskite Lattice through Mn(II) Substitution for Air-Stable Light-Emitting Diodes

All-inorganic cesium lead halide perovskite (CsPbX₃, X = Cl, Br, and I) quantum dots (QDs), possessing high photoluminescence quantum yields and tunable color output, have recently been endowed great promise for high-performance solar cells and light-emitting diodes (LEDs). Although moisture stability has been greatly improved through separating QDs with a SiO₂ shell, the practical applications of CsPbX₃ QDs are severely restricted by their poor thermal stability, which is associated with the intrinsically low formation energies of perovskite lattices. In this regard, enhancing the formation energies of perovskite lattices of CsPbX₃ QDs holds great promise in getting to the root of their poor thermal stability, which hitherto remains untouched. Herein, we demonstrate an effective strategy through Mn²⁺ substitution to fundamentally stabilize perovskite lattices of CsPbX₃ QDs even at high temperatures up to 200 °C under ambient air conditions. We employ first-principle calculations to confirm that the significantly improved thermal stability and optical performance of CsPbX₃:Mn²⁺ QDs arise primarily from the enhanced formation energy due to the successful doping of Mn²⁺ in CsPbX₃ QDs. Benefiting from such an effective substitution strategy, these Mn²⁺-doped CsPbX₃ QDs can function well as efficient light emitters toward the fabrication of high-performance perovskite LEDs.