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🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Shih, Min-HsiungSubject: search.filters.subject.light-emitting diodes (LEDs)

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Now showing 1 - 5 of 5
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    Wide-Range Correlated Color Temperature Light Generation From Resonant Cavity Hybrid Quantum Dot Light-Emitting Diodes
    (2015-07-01)
    Chen, Kuo-Ju
    ;
    Lin, Chien-Chung
    ;
    Han, Hau-Vei
    ;
    Lee, Chia-Yu
    ;
    Chien, Shih-Hsuan
    This study presents extremely uniform colloidal quantum dot white light-emitting diodes (QD-WLEDs) that demonstrate a high color rendering index (CRI) and correlated color temperatures (CCTs) ranging from 2500 to 4500 K. Experimental results indicate that the structure of the distributed Bragg reflector (DBR) containing a stopband in the UV region enhances the intensity output of both monochromatic QD-LEDs and QD-WLEDs by reflecting the unconverted UV light back onto the package to excite the QDs further. Furthermore, the angular CCT uniformity of the QD-WLEDs also improved considerably because of the dependence of the DBR structure on the incident angle. The angular CCT deviation in the range of -70 degrees to 70 degrees decreased to 39 K and the CRI of the WLED is higher than 90. The high-CRI and uniform angular CCT QD-WLED containing the DBR demonstrates potential applicability as the lighting source of next-generation display devices and solid-state lighting.
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    Investigation and Comparison of the GaN-Based Light-Emitting Diodes Grown on High Aspect Ratio Nano-Cone and General Micro-Cone Patterned Sapphire Substrate
    (2013-12-01)
    Huang, Jhih-Kai
    ;
    Lin, Da-Wei
    ;
    Shih, Min-Hsiung
    ;
    Lee, Kang-Yuan
    ;
    Chen, Jyun-Rong
    In this paper, we demonstrated the high performance GaN-based LEDs by using a high aspect ratio cone-shape nano-patterned sapphire substrate (HAR-NPSS). We utilized nano-imprint lithography (NIL) and dry-etching system to fabricate a high depth HAR-NPSS. The micro-scale patterned sapphire substrate (PSS) was also used for comparison. A great enhancement of light output was observed when GaN-based LEDs were grown on a HAR-NPSS or a PSS. The light output power of LEDs with a HAR-NPSS and LEDs with a PSS were enhanced of 49 and 38% compared to LEDs with a unpatterned sapphire substrate. The high output power of the LED with a HAR-NPSS indicated that the technology of NAR-NPSS not only can improve the crystalline quality of GaN-based LEDs but also a promising development to a NPSS.
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    An Investigation of the Optical Analysis in White Light-Emitting Diodes With Conformal and Remote Phosphor Structure
    (2013-11-01)
    Chen, Kuo-Ju
    ;
    Chen, Hsin-Chu
    ;
    Lin, Chien-Chung
    ;
    Wang, Chao-Hsun
    ;
    Yeh, Chia-Chi
    An effective emission model of phosphor film is proposed by using bidirectional scattering distribution function system (BSDF), and the model is verified by white light-emitting diodes (LEDs) with conformal and remote phosphor structure. The emission model is built to clarify the optical characteristics by analyzing the angular-dependent distribution of emission and excitation behaviors in phosphor film. The white LEDs with conformal and remote phosphor structure are also fabricated for experimental comparison. The uniformity of angular correlated color temperature (CCT) in white LEDs can be determined by the angular distribution of blue and yellow light, which is in turns decided by the refractive index variation between chip a (c) nd phosphor layers. Finally, the experimental results are found to have good agreement with the simulation results performing by the Monte Carlo method.
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    Improving the Angular Color Uniformity of Hybrid Phosphor Structures in White Light-Emitting Diodes
    (2013-10-01)
    Chen, Kuo-Ju
    ;
    Han, Hau-Vei
    ;
    Lin, Bing-Cheng
    ;
    Chen, Hsin-Chu
    ;
    Shih, Min-Hsiung
    This letter examines a hybrid phosphor structure for white light-emitting diodes. The hybrid phosphor structure produces more efficient luminosity and more uniform angular correlated color temperature (CCT) than the conventional dispensing method. The experimental results show that the CCT deviation improved from 453 to 280 K between -70 degrees and 70 degrees. This was likely caused by the large blue light divergent angle. The lumen output produced was higher than that produced by dispense and conformal phosphor structures. Therefore, the results show that the hybrid phosphor structure can be used in solid-state lighting.
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    Efficiency and Droop Improvement in Hybrid Warm White LEDs Using InGaN and AlGaInP High-Voltage LEDs
    (2013-04-01)
    Chen, Kuo-Ju
    ;
    Kuo, Hsuan-Ting
    ;
    Chiang, Yen-Chih
    ;
    Chen, Hsin-Chu
    ;
    Wang, Chao-Hsun
    This study investigates the optical and electrical characteristics in hybrid warm white high-voltage light-emitting diodes (HV-LEDs). The luminous efficiency of the hybrid warm white LED in this study improved by 11% and 51%, compared to conventional cool and warm LEDs, respectively, solving the warm white gap in white LEDs. The efficiency droop of the hybrid warm white LED was reduced to 21.8% from 26.8% for the conventional cool white LED, and from 26.3% in the conventional warm white LED at 40 mA (35 A/cm(2)) the operated current. Furthermore, the color rendering index (CRI) and angular correlated color temperature (CCT) were analyzed, indicating a significant improvement in hybrid warm white HV-LEDs.