Direct Integration of Conductive, Emissive Perovskite Nanocrystals Into Efficient Light‐Emitting Diodes Without Post‐Synthetic Ligand Exchange

ABSTRACT Colloidal perovskite nanocrystals (PNCs) have emerged as promising candidates for optoelectronic applications, leveraging their excellent optical, photophysical, and electrical properties combined with solution processability. However, the electrically insulating nature of conventional long‐chain ligands necessitates post‐synthetic ligand exchange for practical device integration. Here, we demonstrate that a synthetically engineered surface chemistry, featuring a low ligand density and robust halide passivation, enables the direct integration of colloidal PNCs into optoelectronic devices without a ligand exchange process. This is achieved by synthesizing CsPbBr 3 PNCs stabilized with Br – instead of anionic oleate ligands. Due to the stronger binding of the OAM/Br − ligand system to the CsPbBr 3 surface, compared to the OAM/oleate system, the resultant PNCs show suppressed surface defect formation and improved optical properties. The reduced surface ligand density allows for higher charge carrier mobility in the PNC thin films relative to their oleate‐capped counterparts. Without post‐synthetic ligand exchange, the colloidal PNCs are directly integrated into light‐emitting diodes, achieving enhanced charge carrier injection and a higher maximum external quantum efficiency of 11.4%, compared to 2.7% for conventional PNC‐based devices.