Browsing by Author "Tseng, Chi-Wei"

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An optimized surface plasmon photovoltaic structure using energy transfer between discrete nano-particles
(2013-01-14)
Lin, Albert
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Fu, Sze-Ming
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Chung, Yen-Kai
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Lai, Shih-yun
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Tseng, Chi-Wei
Surface plasmon enhancement has been proposed as a way to achieve higher absorption for thin-film photovoltaics, where surface plasmon polariton(SPP) and localized surface plasmon (LSP) are shown to provide dense near field and far field light scattering. Here it is shown that controlled far-field light scattering can be achieved using successive coupling between surface plasmonic (SP) nano-particles. Through genetic algorithm (GA) optimization, energy transfer between discrete nano-particles (ETDNP) is identified, which enhances solar cell efficiency. The optimized energy transfer structure acts like lumped-element transmission line and can properly alter the direction of photon flow. Increased in-plane component of wavevector is thus achieved and photon path length is extended. In addition, Wood-Rayleigh anomaly, at which transmission minimum occurs, is avoided through GA optimization. Optimized energy transfer structure provides 46.95% improvement over baseline planar cell. It achieves larger angular scattering capability compared to conventional surface plasmon polariton back reflector structure and index-guided structure due to SP energy transfer through mode coupling. Via SP mediated energy transfer, an alternative way to control the light flow inside thin- film is proposed, which can be more efficient than conventional index-guided mode using total internal reflection (TIR). (C)2012 Optical Society of America
Experimental and Theoretical Study of Low-Cost Hydrothermally Grown Nanowire Silicon Solar Cell
(2013)
Li, Hung-Hsien
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Lin, Albert S.
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Zhong, Yan-Kai
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Fu, Sze-Ming
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Lai, Shih-Yun
The low cost and high absorbance is the two most important considerations for thin-film silicon photovoltaics. In this work, aluminum doped zinc oxide(AZO) nanowire is grown by low cost hydrothermal method and nano-structured amorphous silicon(alpha-Si) solar cell is realized on these AZO nanowire substrate. The experimental result shows superior light trapping property compared to conventional planar structure with 18.83% improvement in photocurrent. Simulation result shows the required thickness for full absorption for high aspect ratio AZO nanowire solar cell is similar to 0.3 square m, much thinner than planar type solar cell. The calculation reveals that solar cell absorbance increases with the nanowire length and packing density, indicating material volume is the first order effect for nanowire solar cells. The proposed low-cost AZO nanowire array amorphous silicon solar cell is very promising for future nanostructured silicon photovoltaics.
Lithographically fabricable, optimized three-dimensional solar cell random structure
(2013-10-01)
Lin, Albert S.
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Zhong, Yan-Kai
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Fu, Sze-Ming
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Tseng, Chi-Wei
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Lai, Shih-Yun
The optimized random reflector is highly preferred for solar cells due to its superiority over an un-optimized totally random surface and its potential to exceed the Lambertian limit. There are some obstacles to overcome for realizing optimized random reflectors, including the feasibility from the process viewpoint and the intensive computational demand for large-scale random reflector design. Here a binary random grating is proposed which can be easily fabricated using common lithographic techniques. By using a global optimization algorithm and three-dimensional (3D) EMW simulation, the solar cell structure with 4 x 4 quasi-random binary grating can provide 23% higher integrated absorbance than its periodic grating counterpart and 103.5% higher integrated absorbance than a planar cell, approaching the Lambertian limit. Broad-band transmission improvement at short wavelength and a broad-band waveguiding effect at long wavelength is observed for the optimized 3D geometry. Additionally, the optimized random grating surpasses the periodic grating at all incident angles. The absorbance of the large-scale, fully optimized binary pattern can potentially exceed the Lambertian limit while its computational demand is shown to be manageable.
Optimization of plasmonic cavity-resonant multijunction cells
(2013-06-01)
Lin, Albert S.
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Fu, Sze-Ming
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Zhong, Yan-Kai
;
Tseng, Chi-Wei
;
Lai, Shih-Yun
Improving spectral photon harvesting is important for thin-film multijunction cells. We show that efficient spectral flux management can be achieved using genetic algorithm-optimized surface plasmon (SP) cavity-resonant type multijunction cells. We also observe that the excitation of the SP quasi-guided mode, Fabry-Perot mode, and SP polariton significantly enhance the photocurrent of multijunction cells. Two types of cavity structures are investigated. For the optimized SP intermediate reflector and bottom-grating cavity, the resonant cavity mode efficiently increases the long-wavelength absorption in the bottom cell by 63.27%, resulting in reduced absorbance asymmetry between the top and the bottom cells. Accordingly, the matched integrated absorbance is increased by 14.92%. For the optimized SP top-and bottom-grating (TBG) cavity, the integrated absorbance and current matching are improved due to the higher transmission through the solar cell front surface and the excitation of the quasi-guided mode with a more localized field in the bottom cell. The matched integrated absorbance is improved by 85.68% for the TBG cavity. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI:10.1117/1.OE.52.6.064002]