Browsing by Author "Huang, Wei-Ming"

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An ultra-compact blackbody using electrophoretic deposited carbon nanotube films
(2018-01-01)
Lin, Albert
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Yang, Chien-Chih
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Parashar, Parag
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Lin, Chien-Yung
;
Jian, Ding Rung
Carbon nanotubes (CNTs) possesses decent optical properties and thus can be considered as a candidate for perfect absorbers due to their close-to-air refractive index and minimal extinction. However, weak absorption in porous materials, due to the low extinction coefficients, requires an inevitably thick absorption layer (similar to 100 mu m) for the perfect opaque absorbers. Thus, the requirement of large thicknesses of CNTs prohibits them from being used as miniaturized integrated photonic devices. Here, we propose an electrophoretic deposited (EPD) CNT resonant cavity structure on tantalum (Ta) to enhance optical absorption. Efficient random light scattering along with the resonant cavity structure using Ti/SiO2 stacking enhances the absorption in our proposed EPD-CNT film while maintaining the total device thickness to <1 mu m. The experiment results reveal that the absorption band covers the entire UV-VIS-NIR spectrum (lambda = 0.3-2.6 mu m), using resonant-cavity EPD-CNT design. The EPD deposition process is done at relatively low temperature < 120 degrees C. We believe that this proposal is very promising for sensing, antenna, and thermophotovoltaics (TPV), in terms of bandwidth, compactness and cost.
Down Shifted Converssion for Enhanceed HIT SSolar Cell Efficiency
(2017-01-01)
Lin, Albert S.
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Parashar, Parag
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Huang, Wei-Ming
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Huang, Yi-Wen
;
Jian, Ding-Rung
In this work, HIT solar cell is incorporated with the luminescent down-shifting (LDS) mechanism for the incident solar spectrum. The heterojunction with intrinsic thin-layer(HIT) solar cell is highly efficient, low temperature (200 C), low cost, and highly symmetrical device. Nevertheless, the carrier collection efficiency is low for the short wavelength solar photons due to the surface recombination. Here, a thin phosphor layer is spray coated on the top of HIT solar cells for the luminescent down-shifting of high energy photons and thus enhanced external quantum efficiency (EQE) for the device for lambda=300nm-450nm is observed.
Lithography-free thin-titanium-nanocone metamaterial perfect absorbers using ZnO nanostructures
(2017-10-01)
Lin, Albert
;
Parashar, Parag
;
Yang, Chih-Chieh
;
Jian, Ding Rung
;
Huang, Wei-Ming
In this work, thin Ti nanocones are deposited on top of the arrays of ZnO nanopagodas, and the whole structure works as an efficient nanostructured metamaterial perfect absorber (MPA) without using lithography and dry etching. In this design, similar to 1 mu m long ZnO nanopagoda arrays are grown on a 100 nm ZnO buffer layer over the silicon/glass substrate by a treatment with an aqueous solution of L-ascorbic acid. Growth direction and the degree of lamination in the ZnO nanostructures can be easily controlled by adjusting the concentration of L-ascorbic acid. Afterward, these ZnO nanopagodas are coated with a 30nm thin top and a 500nm thick bottom layer of Ti to achieve the proposed nanocone resonant cavity structure with electromagnetic wave field penetration. The overall structure encapsulates three physical concepts, namely, field penetration, adiabatic coupling and cavity resonance, which contribute the broadband perfect absorption. The entire process is carried out at a low temperature (< 90 degrees). We believe the proposed tapered Ti nanocones MPA structure facilitates ultra-broadband perfect spectral absorption with promising nature of low-cost, large-area, and lithography-free. (C) 2017 Optical Society of America
Temperature coefficient of diode-connected LTPS poly-Si TFTs and its application on the bandgap reference circuit
(2008)
Lu, Ting-Chou
;
Zan, Hsiao-Wen
;
Ker, Ming-Dou
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Huang, Wei-Ming
;
Lin, Kun-Chih
The temperature coefficient (TC) of n-type diode-connected polycrystalline silicon thin-film transistors (poly-Si TFTs) is investigated. The relationship between TC and the activation energy is observed and explained. It is also found that TC is not sensitive to the deviation of the laser crystallization energy. On the contrary, channel width can effectively modulate TC. By using the diode-connected poly-Si TFTs with different channel widths, a new bandgap reference circuit for precise analog circuit design on glass substrate is proposed and realized. From the experimental results in a LTPS process, the output voltage reference exhibits a very low TC of 195 ppm/degrees C, between 25 degrees C and 125 degrees C.