Stable Green CsPbBr₃ Perovskite Light-Emitting Diodes by Inorganic Metal Ligands

Halide perovskite light-emitting diodes (PeLEDs) have garnered significant research interest, owing to their exceptional optoelectronic properties. Nevertheless, nonradiative recombination processes, primarily induced by intrinsic defects within the material, severely constrain device electroluminescence (EL) efficiency and operational stability, thereby impeding the development of viable applications. To mitigate this challenge, we propose an inorganic metal repairing strategy that employs Zn²⁺ ions from a ZnBr₂ precursor as a CsPbBr₃ perovskite ligand. This approach not only effectively facilitates the crystallization process and enlarges the annealing window but also fills bromine vacancies and coordinates with uncoordinated Pb²⁺ ions with a photoluminescence quantum yield (PLQY) reaching 97%. Importantly, ZnBr₂ treatment contributes to outstanding film quality in terms of pinhole, surface roughness, and trap-state density. Furthermore, ZnBr₂-treated perovskite films exhibit superior stabilities under ambient air, ultraviolet (UV) irradiation, and elevated temperature conditions. Density functional theory (DFT) calculations reveal that these merits arise from more negative perovskite formation energies. Finally, the ZnBr₂-treated PeLEDs present overall enhancement in peak external quantum efficiency (EQE) of 12.3%, maximum luminance of 5322 cd m^-2, and operational lifetime of 556 s, from mere 3.4%, 1569 cd m^-2, and 47 s for the control device, demonstrating enhanced performance and stability.