The effects of surface termination, stoichiometry, and strain on the optical properties of bulk-like ZnSe/ZnS core-shell nanocrystals.

Blue-emitting, cadmium-free quantum dots are increasingly vital for optoelectronic applications such as displays and bio-tagging. In particular, bulk-like ZnSe nanocrystals and core–shell quantum dots—with a thin ZnS shell on a ZnSe core—have emerged as promising candidates for blue-light emission. In this study, we employed an atomistic tight-binding approach to investigate these systems. We examined the influence of anion-cation stoichiometry, with particular emphasis on surface termination, and assessed the effect of shell growth on single-particle and excitonic spectra. Our findings revealed significant spectral differences among dots of nominally identical composition, arising from subtle variations in the anion-cation balance. Notably, we demonstrated that strain in large ZnSe/ZnS nanocrystals induces a blueshift in the emission energy, contrary to the conventional expectation of a redshift. These results provide valuable insights into the spectral engineering of heavy-metal-free quantum dots via precise tailoring of core–shell dimensions.