Hybrid Ligand Engineering for CdSe/CdS Core/Shell Colloidal Nanoplatelets

Colloidal semiconductor nanoplatelets (NPLs) are attractive materials for optoelectronic applications due to their narrow emission linewidths, suppressed Auger recombination and directional emission characteristics. However, the long-chain organic ligands commonly used during synthesis act as insulating barriers, limiting charge transport and compromising device performance. In this work, we develop a hybrid ligand strategy for CdSe/CdS core/shell NPLs that combines inorganic metal halide passivation with organic alkyl amine ligands. In-solution ligand exchange with various metal halide salts enables efficient removal of native oleic acid ligands while preserving the optical and structural integrity of the NPLs. Among the investigated ligands, (NH4)2ZnCl4 provides the most effective inorganic passivation, yielding the highest PLQY among halide-treated samples (15%). Subsequent alkyl amine treatment restores colloidal stability in nonpolar solvents and leads to a substantial recovery of PLQY (60%), approaching that of the as-synthesized NPLs. This hybrid ligand approach offers an effective route toward simultaneously achieving compact surface passivation, high optical efficiency, and solution processability in colloidal NPLs