Rigid Cationic Ligands Enable High-Efficiency NIR-II Photoluminescence in Copper(I) Iodide Hybrid Semiconductors

Abstract

Near-infrared (NIR) luminescent materials are pivotal for advanced optoelectronic and biomedical applications, yet attaining efficient emission in the NIR-II region (950-1400 nm) remains challenging. Here, we introduce a ligand cationization strategy for designing copper(I) iodide-organic hybrid materials that emit in the NIR-II emission (920-1120 nm) with PLQYs up to 8.58%. By incorporating rigid cationic ligands with CuI modules, we synergistically achieve bandgap narrowing (to 1.51 eV) and structural rigidification via ionic-dative bonding, effectively suppressing non-radiative decay while extending emission beyond 1100 nm. Coupled with solution processability—enabled by the successful synthesis of nanometer-sized nanoparticles in various shapes—and excellent thermal stability (≥210 °C), this work establishes ligand cationization as a universal approach for designing efficient NIR-II emitters.