A multifunctional zinc halide enables the synthesis of high-efficiency, color-tunable ZnCuGaSe/ZnS quantum dots for enhanced electroluminescence.

Abstract

I-III-VI quantum dots (QDs) are premier candidates for next-generation lighting and display technologies due to their low toxicity, wide color tunability, and high photoluminescence quantum yields (PLQYs). While tuning the core composition is a well-established method for modulating their properties, the degradation of optical performance caused by insufficient shell growth and poor surface ligand coordination remains under-addressed. Specifically, shell-related defects continue to hinder the optimization of both materials and their resulting quantum-dot light-emitting diodes (QLEDs). In this work, we systematically investigate a zinc halide (ZnX2, where X = I, Cl, Br, F)-mediated shell-engineering strategy to produce high-efficiency, color-tunable ZnCuGaSe/ZnS (ZCGSe/ZnS) QDs. We demonstrate that ZnX2 serves a dual purpose: it promotes the epitaxial growth of the ZnS shell and acts as an X/Z-type ligand to passivate surface defects, effectively suppressing non-radiative recombination. Furthermore, the introduction of ZnX2 regulates the alloying process at the core/shell interface, enabling precise spectral tuning without compromising efficiency. The resulting ZCGSe/ZnS QDs exhibit a finely tunable emission range (525-565 nm) with PLQYs exceeding 94%. QLEDs fabricated using ZnI2 as a shell precursor achieved a maximum luminance (Lmax) of 2152 cd m-2, a maximum external quantum efficiency (EQEmax) of 5.4%, and a stable electroluminescence (EL) peak at 534 nm. This work provides a robust pathway for developing high-performance, eco-friendly I-III-VI QDs for advanced optoelectronic applications.