Browsing by Author "Sun, W. C."

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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.
;
Hsu, M. H.
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Chang, W. L.
;
Sun, W. C.
;
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.
High Efficiency Silicon Solar Cells with Bilayer Passivation Structure
(2009)
Sun, W. C.
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Chang, W. L.
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Chen, C. H.
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Du, C. H.
;
Wang, T. Y.
lThe effects of passivation on monocrystalline silicon solar cells were investigated. Al(2)O(3) and SiO(2) films, prepared by atomic layer deposition and thermal oxidation, respectively, were used as passivation layers. Passivation using a monolayer (SiO(2)) yielded a cell efficiency of 17.5%. However, the Al(2)O(3)/SiO(2) bilayer structure drastically increased cell efficiency to 20.1%. Quantum efficiency results revealed a significant improvement in the IR range, suggesting that bilayer passivation was effective on the back of a solar cell in providing a high energy conversion efficiency. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3194252] All rights reserved.
Indium-Tin-Oxide Nanowhiskers Crystalline Silicon Photovoltaics Combining Micro- and Nano-Scale Surface Textures
(2011)
Chang, C. H.
;
Hsu, M. H.
;
Chang, W. L.
;
Sun, W. C.
;
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.
Novel Indium-Tin-Oxide Nano-Whiskers for Enhanced Transmission of Surface-Textured Silicon Photovoltaic Cells
(2009)
Chang, C. H.
;
Hsu, Min-Hsiang
;
Yu, Peichen
;
Kuo, H. C.
;
Chang, W. L.
Conductive Indium-Tin-Oxide (ITO) nano-whiskers were deposited on surface-textured Si solar cells using glancing-angle electron-beam deposition. With different deposited time, the ITO nano-structured layer exhibit tunable thickness, which can be related to the surface reflectance. The optimized nano-whisker surface demonstrates a broadband anti-reflective properties (R<5%), better than the traditional Si(3)N(4) antireflection coating. Current-voltage and quantum efficiency analyses with the measured reflectivity data show enhanced optical transmission in the long wavelength range from 700nm to 1000nm, corresponding to a conversion efficiency improvement from 13.93% to 14.37%.