Surface Ligand Engineering toward Brightly Luminescent and Stable Cesium Lead Halide Perovskite Nanoplatelets for Efficient Blue-Light-Emitting Diodes

Recently, two-dimensional colloidal perovskite nano platelets (NPLs) have attracted great attention as one of the most promising candidate blue emitters due to their large exciton binding energy and precisely tunable thickness. However, the lack of techniques to simultaneously obtain highly emissive and stable perovskite NPLs has limited the successful exploitation of highly efficient perovskite NPL-based optoelectronic devices. Herein, we report the surface ligand-engineering strategy to enhance the photoluminescence quantum yields and stability of perovskite NPLs using a short-chain halide ion-pair ligand. Benefits from the shorter-chain ligand treatment, the electronic conductivity, and carrier injection of perovskite NPL films have also been improved significantly, enabling us to realize highly efficient blue (469 nm) electroluminescence devices with a peak external quantum efficiency of 1.42%, which is among the highest efficiencies of colloidal pure-bromide perovskite NPL-based light-emitting diodes.