Compositional and Heterostructural Tuning in Red-Emissive Ternary ZnSeTe Quantum Dots for Display Applications

Abstract

II-VI ZnSeTe quantum dots (QDs) are emerging environmentally friendly emitters particularly for blue color while further extendable to green emissivity via Te/Se compositional tuning. However, the realization of red-emissive ZnSeTe QDs becomes highly challenging primarily due to a strong band gap bowing between bulk ZnSe and ZnTe. Herein, a series of ternary ZnSeTe cores with a wide range of nominal Te/Se ratios (0.1-8) were first synthesized and individually subjected to an identical triple shelling with ZnSe inner, ZnSeS intermediate, and ZnS outer shell. Given the pursuit toward efficient red emissivity from ZnSeTe QDs in this work, the Te/Se ratio of 2 is found to be the most suitable in core synthesis, resulting in a photoluminescence (PL) peak of 608 nm and a quantum yield (QY) of 55%. To further enhance their PL performances, an interlayer of ZnSeTe having a lower Te/Se ratio than that of the core is introduced prior to ZnSe shelling. This leads to PL QY enhancement from 55 to 63% along with a PL red-shift from 608 to 612 nm, proving that the Te-less ZnSeTe interlayer is indeed effective in lessening the interfacial strain between the Te-rich ZnSeTe core and the ZnSe inner shell. These emergent ZnSeTe QDs can be potential red emitters, particularly for display devices.