Synthesis, Characterization and Applications of Cadmium-free Light-emitting Semiconducting Quantum Dots
Date Issued
2014
Date
2014
Author(s)
Chuang, Po-Hsiang
Abstract
Semiconductor quantum dots (QDs), whose particle sizes are in the nanometer range, have very unusual optical properties that depend upon the particle size and composition. However, in case of Cadmium-based QDs, Cd is toxic element, which would cause serious restrictions. Therefore, our researches focused on developing non-toxic QDs, which include CuInS2 and InP QDs and their applications. First, we synthesized CuInS2 (CIS) I-III-VI type quantum dots (QDs) under different growth times by the facile solvothermal method. The quantum yield (QY) can be enhanced to 85% by coating ZnS shell at outside of CIS, forming the CIS/ZnS core/shell QDs. CIS/ZnS QDs, show high efficiency and large full width at half-maximum (FWHM). Thus, these non-toxic QDs as light-emitting diodes (LEDs) converters for illumination are a good candidate. We also incorporated red emitting CIS/ZnS QDs into the fabricated white LEDs to improve the color rendering index (CRI) value (Ra = 86). We further synthesized CIS QDs with various [Cu]/[In] ratio by solvothermal method. The band gap and emission energies of CIS QDs are found to be systematically increased with decreasing Cu content. ZnS shell coated of CIS/ZnS core/shell QDs emit quite tunable wavelengths with high QY, depending on the composition. We further investigated the optical properties, lattice structure and thermal stability of CIS and CIS/ZnS core/shell QDs. By combining with high QY CIS/ZnS core/shell QDs as color converters with blue-emitting LEDs and green phosphors Ba2SiO4:Eu2+, the QDs-assisted LEDs with high CRI of near 90 are fabricated. Meanwhile, The potential to use CuInS2/ZnS QDs in LEDs is demonstrated by fabricating electroluminescent devices. We synthesized InP and InP/ZnS QDs and characterized the fluorescence. Additionally, dental resins containing InP QDs as luminophores and in vitro cytotoxicity of InP QDs-embedded resin was investigated by employing human gingival fibroblast cell, showing it’s a good biocompatible for dental material.
Subjects
無鎘
量子點
Type
thesis
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