Browsing by Author "Chen, Hsin Chu"

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A novel randomly textured phosphor structure for highly efficient white light-emitting diodes
(2012-03-16)
Chen, Hsin Chu
;
Chen, Kuo Ju
;
Wang, Chao Hsun
;
Lin, Chien Chung
;
Yeh, Chia Chi
We have successfully demonstrated the enhanced luminous flux and lumen efficiency in white light-emitting diodes by the randomly textured phosphor structure. The textured phosphor structure was fabricated by a simple imprinting technique, which does not need an expensive dry-etching machine or a complex patterned definition. The textured phosphor structure increases luminous flux by 5.4% and 2.5% at a driving current of 120 mA, compared with the flat phosphor and half-spherical lens structures, respectively. The increment was due to the scattering of textured surface and also the phosphor particles, leading to the enhancement of utilization efficiency of blue light. Furthermore, the textured phosphor structure has a larger view angle at the full width at half maximum (87A degrees) than the reference LEDs.
Efficiency Enhancement InGaP/GaAs Dual-Junction Solar Cell with Subwavelength Antireflection Nanorod Arrays
(2011-12-01)
Tsai, Min-An
;
Chen, Hsin Chu
;
Tseng, Ping Chen
;
Yu, Peichen
;
Chiu, Chin Hua
The enhanced conversion efficiency of the InGaP/GaAs dual-junction solar cell was demonstrated utilizing broad-band and omnidirectional antireflection nanorod arrays. The nanorod arrays were fabricated by self-assembled Ni clusters, followed by inductively-coupled-plasma reactive ion etching. The conversion efficiency measured under one-sun air mass 1.5 global illuminations at room temperature was improved by 10.8%. The light absorption efficiencies of the top InGaP and bottom GaAs cells were also studied under the influence of nanorod arrays. The enhanced absorption efficiency was mostly contributed from the short wavelength absorption by top cell. Surface nanorod arrays served not only as broad-band omnidirectional antireflection layers but also scattering sources. The structure can be further optimized to obtain the maximum conversion efficiency.
Spectrally Dependent Performance of Hybrid Colloidal Quantum Dots GaAs Solar Cells
(2013)
Han, Hau-Vei
;
Lin, Chien-Chung
;
Chen, Hsin Chu
;
Tsai, Yu-Lin
;
Yeh, Yun-Ling
Because of the global warming effect and energy crisis, the usage of solar energy gets more and more important in recent years. In particular, GaAs-based solar cells have been regarded as a promising candidate to provide high power conversion efficiency because of their direct band gap and strong absorption over the entire visible part of the solar spectrum. In this work, we demonstrate a hybrid design of traditional GaAs-based solar cell combined with colloidal quantum dots. Several photovoltaic parameters were enhanced, including the short circuit current density, fill factor, and power conversion efficiency, which were measured under white light illumination similar to the solar spectrum. With anti-reflective feature at long wavelength and down-conversion at high energy photons, the quantum dot effectively enhance the overall power conversion efficiency by as high as 25% compared to traditional GaAs-based device. The evolution of short-circuit current density and weighted reflectance as a function of the dilution factor of three type QDs has been investigated. The dilution factors of quantum dots solution also have been optimized for single junction GaAs devices. We also use the EQE enhancement spectrum to further distinguish between the photon down-conversion and antireflection capability of QDs. Finally, we believe this technology shall be a great candidate for next generation of highly efficient photovoltaic devices.