Browsing by Author "Kuo, H. T."

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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.
;
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.
Efficiency and Droop Improvement in GaN-Based High-Voltage Light-Emitting Diodes
(2011-08-01)
Wang, C. H.
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Lin, D. W.
;
Lee, C. Y.
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Tsai, M. A.
;
Chen, G. L.
The efficiency and electrical characteristics of GaN-based high-voltage light-emitting diodes (HV-LEDs) are investigated in detail. The spatial distribution of light output and simulation results showed that 100-V HV-LED with smaller microchips had superior current spreading. As a result, under 1-W operation, the luminous efficiency of 100-V HV-LED with smaller microchips was enhanced by 7.8% compared to that of 50-V HV-LED, while the efficiency droop behaviors were reduced from 28% in 50-V HV-LED to 25.8% in 100-V HV-LED. Moreover, smaller microchips exhibited lower series resistance and forward voltage, leading to higher wall-plug efficiency.