Browsing by Author "Huang, Wei-Lun"

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Effect of Washing Solvents on the Properties of Air-Synthesized Perovskite CsPbBr3 Quantum Dots for Quantum Dot-Based Light-Emitting Devices
(2020-01-01)
Chen, Lung-Chien
;
Tien, Ching-Ho
;
Tseng, Po-Wei
;
Tseng, Zong-Liang
;
Huang, Wei-Lun
In order to improve the stability and cost of perovskite CsPbBr3 and establish a preparation process for quantum dot materials with excellent luminescence properties, CsPbBr3 quantum dots were synthesized by the hot injection method and the ice bath method in air ambient. Then, a proprietary purification system was used to improve the properties of the quantum dots and prepare high-quality perovskite quantum dot films. Optimal material and light characteristics were exhibited with ethyl acetate:hexane as the purification solvent. In the solution form, the photoluminescence wavelength could be maintained at 508 nm with almost no shift compared with other conditions, and the quantum yield could reach 99%; however, superior performance was obtained in the thin-film form, which exhibited little to no shift in the photoluminescence wavelength and, surprisingly, achieved a quantum yield of 91.6% with a narrow PL emission with a full width at half-maximum of 28 nm. In addition, exceptional thin-film uniformity was observed from scanning electron microscopy image analyses. The CsPbBr3 quantum dot light-emitting diode purified with ethyl acetate:hexane demonstrated an open-circuit voltage of 4 V, a maximum luminous brightness of 488 cd m(-2), and a maximum external quantum efficiency of 0.14%.
Exciton Localization of High-Quality ZnO/MgxZn1-x Multiple Quantum Wells on Si (111) with a Y2O3 Buffer Layer
(2018-08-01)
Liu, Wei-Rein
;
Huang, Wei-Lun
;
Wu, Yung-Chi
;
Lai, Liang-Hsun
;
Hsu, Chia-Hung
We report the structural and optical properties of ten-period ZnO/MgxZn1-x multiple quantum wells (MQWs) prepared on the most widely used semiconductor material, Si. The introduction of a nanometer thick high-k Y2O3 transition layer between Si (111) substrate and a ZnO buffer layer significantly improves the structural perfection of the MQWs grown on top of it. The high structural quality of the ZnO/MgxZn1-xO MQWs is evidenced by the appearance of pronounced high order satellite peaks in X-ray crystal truncation rods; high resolution cross-sectional transmission electron microscopy images also confirmed the regularly arranged well and barrier layers. When the well width is less than similar to 2.7 nm, the quantum-confined Stark effect in MQWs can be negligible. Not only the increasing exciton-binding energy but also reducing exciton-phonon coupling determined in temperature-dependent photoluminescence spectra indicate quantum-size effect. Our results demonstrate that ZnO/MgxZn1-xO MQWs integrated on Si have great potential in UV optoelectronic device applications.