Improved Resistance to Photoinduced Quenching in CuInS₂/ZnS Near-Infrared Quantum Dots through Al-Doped Shell Engineering

CuInS₂ (CIS) near-infrared (NIR) quantum dots (QDs) are a promising class of colloidal nanocrystals due to their low toxicity and unique optical properties, making them ideal for a variety of applications. However, their stability, particularly against photoinduced quenching, has been insufficiently studied. Shell doping has emerged as an effective strategy to enhance stability, but existing shell growth methods often lead to significant cation exchange at the core-shell interface, causing an undesirable blue shift in the emission peak and reducing the economic value of NIR emissions. In this study, we introduce a simple and robust shell doping strategy to form a rigid ZnS shell doped with Al, aiming to improve the stability of QDs while preserving their NIR emission. Al doping increases the shell bandgap, enhances quantum confinement, and passivates trap states at the core-shell interface, synergistically boosting optical performance and stability under high excitation power densities. The resulting CIS/AlZnS (CIS/AZS) core/shell QDs exhibit a NIR emission peak at 970 nm, a photoluminescence quantum yield (PL QY) of 95.2%, and significant improvements in stability, including a 100% increase in thermal stability and a 150% enhancement in resistance to photoinduced quenching.