Emission Mechanism of Bright and Eco-Friendly ZnSeTe Quantum Dots

The heavy-metal-free ZnSeTe quantum dots (QDs) hold great promise for the development of modern optoelectronic devices, yet, the nature of the emissive state within remains elusive. Herein, the different emission origins are clarified for the ZnSeTe QDs with dilute and heavy Te contents based on multiple spectroscopic characterizations and first-principles calculation. In the case of dilute Te incorporation (Te/Se < 20%), the low-energy tail of the asymmetric emission is ascribed to the recombination from the localized state induced by Te clusters, and the the hot carrier localization process occurs within a timescale of approximate to 500 fs. As the Te/Se ratio increases above 20%, the charge density difference shows a uniform distribution due to the decrease in electronegativity contrast, such that the carriers become delocalized and tail emission disappears. Meanwhile, the emission line-width broadens mainly originating from the inhomogeneous broadening effect. These findings are constructive for developing sustainable QDs toward optoelectronic applications.