Researchers from Hanyang University, Ajou University and POSTECH have developed a hydrolysis-assisted ligand-exchange strategy that significantly improves charge transport and efficiency in metal halide perovskite nanocrystal (MHP NC) LEDs, achieving a record external quantum efficiency (EQE) of 31.7% for green-emitting devices. Schematic illustration of the ligand-exchange and surface-functionalization process of MHP NCs. Image from: Advanced Materials MHP nanocrystals are widely considered promising candidates for next-generation light-emitting diodes due to their excellent color purity and high radiative efficiency. However, their performance has been limited by the presence of long-chain native ligands on the nanocrystal surface. These ligands are weakly bound and electrically insulating, which hinders charge injection and transport, introduces trap states, and ultimately leads to energy losses in devices. To address these challenges, the researchers introduced a multifunctional π-conjugated pyridine carboxamide (PCA) ligand via a hydrolysis-assisted, one-step ligand-exchange process. This approach removes the original insulating ligands under mild conditions and replaces them with PCA, which provides multidentate, multisite surface coordination. The ligand acts as a strong anchoring group while simultaneously enabling enhanced electronic coupling between nanocrystals and inducing n-type surface functionalization.
Researchers develop new ligand strategy enabling 31.7% EQE perovskite nanocrystal LEDs
