Electroluminescence of Perovskite Nanocrystals with Ligand Engineering

Light-emitting diodes (LEDs) based on metal halide perovskite nanocrystals (MHP NCs) have been rapidly developed to reach external quantum efficiencies of up to 22% with their defect-tolerant nature and extremely high color purity (full width half maxima <25 nm) that are superior to traditional inorganic colloidal quantum dots. However, highly dynamic binding of ligands impedes further increase in efficiency and induces intrinsic instability. In this review, we discuss the light emission in MHP NCs, surface chemistry regarding the surface termination of MHP crystal, and the binding of ligands to crystals. We also discuss strategies to overcome the instability of ligands to improve efficiency and stability of MHP NCs and finally achieve high efficiency of their LED devices.