Browsing by Author "Chen, K. J."

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A Full-Color, White Light Emission of Quantum-Dot-Based Display Technology Using Pulsed Spray Method with Distributed Bragg Reflector
(2012)
Chen, K. J.
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Chen, H. C.
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Lin, C. C.
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Tsai, H. H.
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Tsai, K. A.
A colloidal quantum dot light-emitting multi-layer structure with HFO2/SiO2 distributed Bragg reflector is manufactured by pulse spray method. A pure white light with strong enhancement due to better utilization of UV pump was demonstrated. (C)2012 Optical Society of America
Controlled density growth of carbon nanotubes and its improvement on field emission properties
(2004)
Juan, C. P.
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Tsai, C. C.
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Chen, K. J.
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Hong, W. K.
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Lin, K. C.
The density distribution of the CNTs is one of the crucial parameters for the field emission property of CNTs.We use an inactive thin film layer that was deposited on the catalyst to effectively control the density of the CNTs. The results showed the improved field emission property could be obtained with a thin SiO layer on the catalyst layer as the precursor. For the 3.5 nm Fe and 3.5 nm SiO on 3.5 nm Fe as the catalyst, the turn-on field can be reduced from 3.7 V/ mu m. to 2.2 V/ mu m and the field emission current density increased from 2.6x 10(-8) A/cm(2) to 2.4x 10(-4) A/cm(2) when the applied field was 4 V/mu m. The extremely low turn-on field of 1.3 V/ mu m was also discovered for the CNTs grown with the precursor contained 1.5 nm SiO on 1.5 nm Fe; the extremely high emission current density of 4x 10(-2) A/cm(2) was also achieved under the low electric field of 3.5 V/ mu m.
Design and fabrication of a InGaN vertical-cavity surface-emitting laser with a composition-graded electron-blocking layer
(2014-08-01)
Lin, B. C.
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Chang, Y. A.
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Chen, K. J.
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Chiu, C. H.
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Li, Z. Y.
In this study, the design and fabrication of a InGaN vertical-cavity surface-emitting laser (VCSEL) with a composition-graded electron blocking layer (GEBL) are revealed experimentally and theoretically. It has been demonstrated that laser output performance is improved by using a GEBL when compared to the typical VCSEL structure of a rectangular EBL. The output power obtained at 20 kA cm(-2) is enhanced by a factor of 3.8 by the successful reduction of threshold current density from 12.6 to 9.2 kA cm(-2) and the enlarged slope efficiency. Numerical simulation results also suggest that the improved laser output performances are due mainly to the reduction of electron leakage current and the enhanced hole injection efficiency in the multiple-quantum-well (MQW) active region.
Effect of the Thermal Characteristics of Phosphor for the Conformal and Remote Structures in White Light-Emitting Diodes
(2013-10-01)
Chen, K. J.
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Lin, B. C.
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Chen, H. C.
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Shih, M. H.
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Wang, C. H.
The influence of the thermal effect of phosphor for conformal and remote structures in white light-emitting diodes was investigated using the junction and phosphor temperatures. Comparing the measured temperatures with IR thermometer, the remote structure has a higher phosphor temperature than the conformal structure. This result indicates that the phosphor in the conformal structure has demonstrated superior conduction because of the high thermal conductivity in surrounding. Furthermore, thermal distribution in the simulation results has shown to have favorable agreement with the experimental results. Consequently, the lifetime measurement is shown to verify the results of the simulation and experiment for both structural types.
Excellent Color Rendering Index Quantum Dots White Light-Emitting Diode with Distributed Bragg Reflector Structure
(2014)
Chen, K. J.
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Lin, B. C.
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Han, H. V.
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Lin, C. C.
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Lee, C. Y.
This study demonstrated the high CRI and excellent uniformity colloidal quantum dot white-light-emitting diodes with the DBR structure at different correlated color temperature from 2500 K to 4500K.
Highly Efficient GaAs Solar Cells with Dual Layer of Quantum Dots And A Flexible PDMS Film
(2012)
Lin, Chien-chung
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Chen, H. C.
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Chen, K. J.
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Han, H. V.
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Kuo, H. C.
High performance of GaAs solar cell with dual layer quantum dots separated by flexible polydimethylsiloxane film was demonstrated. By this scheme, the efficiency increased by 22 %, compared to the cell without QDs. (C) 2012 Optical Society of America
Hybrid White Light-emitting Diodes by Organic-Inorganic materials
(2015)
Chen, K. J.
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Lai, Y. C.
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Lin, B. C.
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Lin, C. C.
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Chiu, S. H.
This study demonstrated the high uniformity hybrid white light-emitting didoes with polyfluoren (PFO) polymer and quantum dot (QD) with different CCT range from 3000K to 9000K.
Improvement of Angular-dependent CCT Uniformity by ZrO2 Nano-particles in Remote Phosphor White LEDs
(2012)
Chen, H. C.
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Chen, K. J.
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Wang, C. H.
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Tsai, H. H.
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Lin, C. C.
The superior uniformity of angular-dependent CCT white LEDs have been investigated by ZrO2-type remote phosphor structure. This novel structure reduces angular-dependent CCT deviations from 1000K to 420K in range of -70 to 70 degrees. (C)2012 Optical Society of America
Improvement of lumen efficiency in white light-emitting diodes with air-gap embedded package
(2012-05-01)
Chen, H. C.
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Chen, K. J.
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Lin, C. C.
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Wang, C. H.
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Yeh, C. C.
In this paper, white light-emitting diodes (LEDs) with air-gap embedded package were proposed and fabricated by a simple method including pulsed spray coating. The lumen efficiency of air-gap embedded LED was enhanced by 8.8% at driving current of 350 mA, compared to conventional remote phosphor white LED. This improvement was due to the enhanced utilization of blue and yellow rays, which were confirmed by pulse current-dependent correlated color temperature (CCT). The utilization efficiency of blue rays was enhanced by 12.4% due to the embedded air-gap layer. The simulation results performed by Monte-Carlo ray tracing method agreed with our experiments, which showed enhancement in lumen efficiency and similar CCT. Finally, the electric field intensity versus different thickness for air-gap and no air-gap embedded white LED was calculated to check the incident blue rays trapped in phosphor layer. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.
Normally-off operation AlGaN/GaN MOS-HEMT with high threshold voltage
(2010-09-02)
Chang, C. -T.
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Hsu, T. -H.
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Chang, E. Y.
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Chen, Y. -C.
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Trinh, H. -D.
Normally-off operation AlGaN/GaN high electron mobility transistors have been developed utilising a fluorine-based treatment technique combined with a metal-oxide-semiconductor gate architecture. Threshold voltage as high as 5.1 V was achieved by using an 16 nm-thick Al(2)O(3) gate oxide film. Additionally, the device performed a drain current density of 500 mA/mm and a peak transconductance of 100 mS/mm, which are comparable to the conventional normally-on devices.