Browsing by Author "Yeh, Chia-Chi"

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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.
Patterned structure of REMOTE PHOSPHOR for phosphor-converted white LEDs
(2011-07-04)
Kuo, Hao-Chung
;
Hung, Cheng-Wei
;
Chen, Hsin-Chu
;
Chen, Kuo-Ju
;
Wang, Chao-Hsun
High efficiency white light-emitting diodes with superior color-mixing have been investigated. It is suggested that the patterned remote phosphor structure could improve the uniformity of angular-dependent correlated color temperature (CCT) and achieve high chromatic stability in wider operating current range, as compared to the conventional remote phosphor coating structure. In this experiment, we employed a pulse spray coating method to place the patterned phosphor on the package and to leave a window region. The window area, a clear space without coating of the phosphor not only increases the extraction efficiency of blue rays at large angle, but also improves the stability of angular-dependent CCT. Moreover, the CCT deviation could be reduced from 1320 K to 266 K by this patterned remote phosphor method, and the stray blue/yellow light within the package can be effectively reduced and controlled. The design was verified both experimentally and theoretically. (C) 2011 Optical Society of America