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.
Highlights
Nanometer-scaled semiconductor materials called quantum dots (QDs) exhibit sizedependent electronic and optical properties due to the quantum confinement effect that is generated from spatially driven charge carriers, including holes and electrons in the ground and excited states [1,2,3]
QDs, we investigated the effects of reaction time and temperature on the PL properties of the ZnSe QDs
We investigated the applicability of the ZnSe/ZnS C/S QDs to white light-emitting diodes (LEDs)
Summary
Nanometer-scaled semiconductor materials called quantum dots (QDs) exhibit sizedependent electronic and optical properties due to the quantum confinement effect that is generated from spatially driven charge carriers, including holes and electrons in the ground and excited states [1,2,3]. There is growing demand to develop cadmium-free QDs to reduce environmental harm and human health issues [11] Related to these issues, cadmium-free green- or red-light-emitting materials, such as InP, CuInS2 , Si-based QDs, and carbon dots, have been studied as alternatives to CdSe QDs [12,13,14,15]. C/S QDs were combined to fabricate white LEDs. The CuInS2 -based QDs are suitable for white LED applications thanks to their high chemical stability, non-toxicity, tunable emitting wavelength, high luminous efficiency, large optical absorption coefficient, and large Stokes shift [30,31]. The CuInS2 -based QDs are suitable for white LED applications thanks to their high chemical stability, non-toxicity, tunable emitting wavelength, high luminous efficiency, large optical absorption coefficient, and large Stokes shift [30,31] For these reasons, CuInS2 /ZnS-based QDs were adopted as the yellow-emitting materials. This study demonstrated that the ZnSe/ZnS QDs are promising for use as a color-converting material for the fabrication of white LEDs
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