Synthesis of Cu─In─S Quantum Dots Through Precursor Activity Optimization for High-Performance Near-Infrared Light Emitting Diodes

Near-infrared quantum dot light-emitting diodes (NIR-QLEDs) hold great promise for optoelectronic applications. However, their low luminous efficacy and poor stability restrict their practical use. This study addresses these challenges by synthesizing environment-friendly Cu─In─S (CIS) quantum dots (QDs) using diisopentyl sulfide to enhance the reactivity of the In precursor. The resulting QDs produce a photoluminescence quantum yield (PLQY) of 40.0%. High-quality QDs are obtained by coating with a ZnS shell, resulting in a PLQY of 93.3%. Photoluminescence analysis reveals that the luminescence mechanism is predominantly governed by donor–acceptor pair recombination. The incorporation of VOC₂O₄ as a hole injection layer into NIR-QLEDs prepared from the QDs enhances hole injection and reduces efficiency roll-off, leading to a peak external quantum efficiency of 17.6%, the highest reported for NIR-QLEDs with emissions exceeding 800 nm. Impedance spectroscopy confirms improved charge injection and transport characteristics. This work underscores the critical role of material synthesis and device architecture in optimizing the performance of NIR-QLEDs for practical applications.