Synergistic NH 4 F and ZnCl 2 -assisted surface engineering enables efficient red ZnSeTe quantum dots for QLEDs

Abstract

ZnSeTe quantum dots (QDs), which exhibit tunable emission across the visible spectrum and enable spatial carrier separation as well as effective bandgap narrowing through band bending and the formation of type-II heterostructures between different shells, are promising candidates for full-color QLED displays; however, their red emission remains low, and red ZnSeTe-based QLEDs have not yet been reported. Herein, we propose a synergistic surface-modification strategy using NH4F and ZnCl2 to enhance the luminescent performance of red-emitting ZnSeTe QDs and enable red QLED fabrication. During core synthesis, F- released from NH4F passivates surface dangling bonds and suppresses defect-related emission. In parallel, ZnCl2 compensates surface metal vacancies, optimizes the interfacial chemical environment, and promotes uniform ZnSe shell growth. These treatments mitigate deep-level traps induced by high Te content, thereby improving crystal quality and increasing the photoluminescence quantum yield (PL QY). The optimized ZnSeTe/ZnSeTeinner/ZnSe/ZnS core/shell QDs exhibit red emission centered at 615 nm with a PL QY of 24.8%, which is higher than that of QDs treated with either additive alone. As a proof of concept, we demonstrate the first red ZnSeTe-based QLEDs reported in the open literature, achieving a maximum luminance of 117 cd m-2 and an external quantum efficiency of 0.3%. These results indicate that the proposed synergistic surface-modification strategy provides a practical route toward high-performance red ZnSeTe QLEDs.