Enhanced performance of cesium copper halide nanocrystal light-emitting diodes via post-treatment induced phase regulation

Cesium copper halides have attracted increasing attention for light-emitting diodes (LEDs) applications due to their high photoluminescence quantum efficiency (PLQE) and non-toxicity. However, the current film fabrication methods for copper halides cannot simultaneously meet the high-performance, eco-friendly, and good environmental tolerance requirements. Here, we demonstrate a facile approach that combines the advantages of both traditional nanocrystal-based methods and precursor solution-based methods. Through treating Cs₃Cu₂I₅ nanocrystal films with proper alcohols, Cs₃Cu₂I₅/CsCu₂I₃ mixed-dimensional copper halides are formed with enhanced PLQE and improved energy level matching. This enhances the peak EQE of copper halide LEDs to 0.8%, which is among the highest efficiency of lead-free metal halide nanocrystal LEDs. This work provides a new strategy for fabricating high-performance lead-free LEDs in an eco-friendly manner.