Phosphine-Free-Synthesized ZnSe/ZnS Core/Shell Quantum Dots for White Light-Emitting Diodes

Abstract

Blue-light-emitting ZnSe core (C) and ZnSe/ZnS core/shell (C/S) quantum dots (QDs) were synthesized with phosphine-free precursors by a thermal decomposition method in paraffin oil solvent and applied to QD-converted light-emitting diodes (LEDs). The optical properties of the synthesized ZnSe C and ZnSe/ZnS C/S QDs were characterized by absorption spectroscopy and photoluminescence spectroscopy. Additionally, the quantum efficiency of the QDs was investigated. Their structural properties were studied with X-ray crystallography and transmission electron microscopy. The ZnSe/ZnS C/S QDs showed deep-blue light peaking at 425 nm. The blue-light-emitting ZnSe/ZnS C/S QDs were used as color-converting materials for near-ultraviolet LED-pumped blue LEDs and combined with yellow-light-emitting Zn-Cu-In-S/ZnS C/S QDs to fabricate white LEDs. The white LEDs showed warm white light [(CIE x, CIE y) = (0.4088, 0.3987)], Tc = 3488 K, and Ra = 61.2]. The results indicate that the ZnSe/ZnS C/S QDs have good potential for white light application after further improvements to their optical properties.

Eco-Friendly Electrophoretic Deposition of Fluorescent Nanocomposite Films in an Aqueous Dispersion of Hydrophilized Core/Shell CuInS2/ZnS Quantum Dots for Optoelectronic Applications

“…Core/shell CIS/ZnS QDs exhibiting up to 97% FLQY have been reported . They are attractive for various applications such as white light-emitting diodes (LEDs), solar cells, and bioimaging due to their low toxicity and excellent visible FL properties. − …”

Reaction-dependent optical behavior and theoretical perspectives of colloidal ZnSe quantum dots

“…However, Cd is toxic, which limits the practical applications these QDs and raises concerns about their potential threats to the environment and human health 3 , 5 . Therefore, there is increasing demand for the development of Cd-free QDs 6 . ZnSe, an important II–VI semiconductor material with a wide bandgap of 2.7 eV and low toxicity, shows promise as a replacement for Cd-based QDs 7 .…”

“…So far, monodispersed ZnSe nanocrystals have been successfully prepared by various solution-based methods, including hot-injection and heating methods 12 . In the hot-injection method, a reagent is injected into a hot reaction solution at room temperature, causing burst homogeneous nucleation, followed by slow growth of the QDs 6 . Moreover, other studies have been reported that Zn/Se ratios that differ from 1:1 do not result in improved optical properties of ZnSe QDs 13 , 14 .…”