Browsing by Author "Hsu, M. H."

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ENHANCED ANGULAR RESPONSE OF POWER CONVERSION EFFICIENCY FOR SILICON SOLAR CELLS UTILIZING A UNIFORMLY DISTRIBUTED NANO-WHISKER MEDIUM
(2010)
Chang, C. H.
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Hsu, M. H.
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Chang, W. L.
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Sun, W. C.
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Wu, C. W.
In the research of photovoltaic devices, eliminating Fresnel reflection loss is a critical issue on the way to pursue higher efficiency. To maximize the power conversion efficiency, dielectric anti reflective coating shows a cost-effective approach, but not enough to absorb broadband solar radiation effectively. Recently, the functional nanostructure shows high potential to be an omnidirectional anti reflective coating for the photovoltaic devices. Here we demonstrate Indium-Tin-Oxide (ITO) nano-whiskers, grown by the self-catalyst vapor-liquid-solid (VLS) mechanisms on the textured Si substrate. The ITO nano-whiskers can provide broadband anti-reflective properties (R < 5%) in the wavelength range of 350-1100nm. In comparison with conventional Si solar cell, the ITO nano-whiskers coating solar cell shows higher external quantum efficiency (EQE) in the range of 700-1100nm. Moreover, the ITO nano-whisker coating Si solar cell shows a high total efficiency increase of 1.1% (from 16.08% to 17.18%). The angular response of the conversion efficiency also increases from 7% at the normal incidence to more than 15% for incident angles over 70 degrees.
Enhanced Omnidirectional Photon Coupling via Quasi-Periodic Patterning of Indium-Tin-Oxide for Organic Thin-Film Solar Cells
(2011-01-01)
Tseng, P. C.
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Hsu, M. H.
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Chen, H. C.
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Tsai, M. A.
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Yu, Peichen
Enhanced optical coupling with respect to all incident angles via an indium tin oxide quasi-periodic structure (ITO-QPS) for organic thin-film solar cells was demonstrated. The cell @2010 Optical Society of America
Fabrication and low temperature thermoelectric properties of NaxCoO2 (x=0.68 and 0.75) epitaxial films by the reactive solid-phase epitaxy
(2007-02-05)
Chang, W. J.
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Hsieh, C. C.
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Chung, T. Y.
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Hsu, S. Y.
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Wu, K. H.
The authors have fabricated NaxCoO2 thin films via lateral diffusion of sodium into Co3O4 (111) epitaxial films (reactive solid-phase epitaxy [Ohta , Cryst. Growth Des. 5, 25 (2005)]). The environment of thermal diffusion is key to the control of the sodium content in thin films. From the results of x-ray diffraction and in-plane rho(ab), the epitaxial growth and the sodium contents of these films were identified. The thermoelectric measurements show a large thermoelectric power similar to that observed in single crystals. The quasiparticle scattering rate is found to approach zero at low temperatures, consistent with the small residual resistivity, indicating high quality of the NaxCoO2 thin films. (c) 2007 American Institute of Physics.
Indium-Tin-Oxide Nanowhiskers Crystalline Silicon Photovoltaics Combining Micro- and Nano-Scale Surface Textures
(2011)
Chang, C. H.
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Hsu, M. H.
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Chang, W. L.
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Sun, W. C.
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Yu, Peichen
In this work, we present a solution that employs combined micro- and nano-scale surface textures to increase light harvesting in the near infrared for crystalline silicon photovoltaics, and discuss the associated antireflection and scattering mechanisms. The combined surface textures are achieved by uniformly depositing a layer of indium-tin-oxide nanowhiskers on passivated, micro-grooved silicon solar cells using electron-beam evaporation. The nanowhiskers facilitate optical transmission in the near-infrared, which is optically equivalent to a stack of two dielectric thin-films with step- and graded- refractive index profiles. The ITO nanowhiskers provide broadband anti-reflective properties (R < 5%) in the wavelength range of 350-1100nm. In comparison with conventional Si solar cell, the combined surface texture solar cell shows higher external quantum efficiency (EQE) in the range of 700-1100nm. Moreover, the ITO nanowhisker coating Si solar cell shows a high total efficiency increase of 1.1% (from 16.08% to17.18%). Furthermore, the nanowhiskers also provide strong forward scattering for ultraviolet and visible light, favorable in thin-wafer silicon photovoltaics to increase the optical absorption path.
Oblique electron-beam evaporation of distinctive indium-tin-oxide nanorods for enhanced light extraction from InGaN/GaN light emitting diodes
(2009-11-09)
Chiu, C. H.
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Yu, Peichen
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Chang, C. H.
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Yang, C. S.
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Hsu, M. H.
This paper presents a novel and mass-producible technique to fabricate indium-tin-oxide (ITO) nanorods which serve as an omnidirectional transparent conductive layer (TCL) for InGaN/GaN light emitting diodes (LEDs). The characteristic nanorods, prepared by oblique electron-beam evaporation in a nitrogen ambient, demonstrate high optical transmittance (T>90%) for the wavelength range of 450nm to 900nm. The light output power of a packaged InGaN/GaN LED with the incorporated nanorod layer is increased by 35.1% at an injection current of 350mA, compared to that of a conventional LED. Calculations based on a finite difference time domain (FDTD) method suggest that the extraction enhancement factor can be further improved by increasing the thickness of the nanorod layer, indicating great potential to enhance the luminous intensity of solid-state lighting devices using ITO nanorod structures. (C) 2009 Optical Society of America
Optical properties of Na0.68CoO2 thin film
(2007)
Hsu, M. H.
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Liu, H. L.
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Chang, W. J.
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Lin, J. Y.
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電子物理學系
The optical reflectance of single-crystalline Na0.68CoO2 (thickness around 3000 angstrom) thin film has been measured over a wide frequency (40-55000 cm(-1)) and at temperatures between 20 and 300 K. The room-temperature optical conductivity spectrum displays a metallic character. In addition, one E-1u phonon mode at about 518 cm(-1) is identified, while the other four phonon peaks are due to the sapphire substrate. As the temperature is lowered, the Drude plasma frequency exhibits little temperature dependence, whereas the scattering rate monotonically decreases with decreasing temperature. Notably, the Drude scattering rate at 20 K is found to approach zero, consistent with the small residual resistivity, indicating high quality of Na0.68CoO2 thin film. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.