Insights from core/shell ZnCuInS/ZnS nanocrystals, type-II confinement, and implications for the design of safer industrial nanocrystals

In this study, we used an atomistic empirical tight-binding approach to systematically investigate the structural, electronic, and optical properties of cadmium-free ZnCuInS/ZnS core/shell nanocrystals over a wide range of core sizes, shell thicknesses, and core compositions. Starting with binary core systems (pure InS and CuS), we extended our analysis to alloyed cores, including Zn1-xInxS and Zn1-xCuxS, and to ternary ZnCuInS cores with varying copper (Cu)/indium (In) ratios. Our results showed that these nanostructures exhibited rich and diverse physical behaviors strongly dependent on composition and geometry. The introduction of In and Cu into ZnCuInS cores allowed for compositional tuning, providing control over key properties such as band gap energy, optical transition strength, and exciton-exciton interactions. To address the limitations of traditional confinement classification schemes, we introduced a set of complementary ways that quantify electron–hole overlap and spatial separation. These approaches provide deeper insight into the nature of exciton localization and facilitate the rational design of nanocrystals with tailored optoelectronic properties. Overall, our study demonstrates that atomistic modeling of ZnCuInS/ZnS nanocrystals provides a powerful method to engineer quantum dot performance through compositional and geometric optimization, paving the way for advanced applications in photonics, optoelectronics, and nanosafety.