Browsing by Author "Tseng, Chi Wei"

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Aperiodic and randomized dielectric mirrors: alternatives to metallic back reflectors for solar cells
(2014-05-05)
Lin, Albert
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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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Yan, Sheng Lun
Dielectric mirrors have recently emerged for solar cells due to the advantages of lower cost, lower temperature processing, higher throughput, and zero plasmonic absorption as compared to conventional metallic counterparts. Nonetheless, in the past, efforts for incorporating dielectric mirrors into photovoltaics were not successful due to limited bandwidth and insufficient light scattering that prevented their wide usage. In this work, it is shown that the key for ultra-broadband dielectric mirrors is aperiodicity, or randomization. In addition, it has been proven that dielectric mirrors can be widely applicable to thin-film and thick wafer-based solar cells to provide for light trapping comparable to conventional metallic back reflectors at their respective optimal geometries. Finally, the near-field angular emission plot of Poynting vectors is conducted, and it further confirms the superior light-scattering property of dielectric mirrors, especially for diffuse medium reflectors, despite the absence of surface plasmon excitation. The preliminary experimental results also confirm the high feasibility of dielectric mirrors for photovoltaics. (C)2014 Optical Society of America
Approaching conversion limit with all-dielectric solar cell reflectors
(2015-02-09)
Fu, Sze Ming
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Lai, Yi-Chun
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Tseng, Chi Wei
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Yan, Sheng Lun
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Zhong, Yan Kai
Metallic back reflectors has been used for thin-film and wafer-based solar cells for very long time. Nonetheless, the metallic mirrors might not be the best choices for photovoltaics. In this work, we show that solar cells with all-dielectric reflectors can surpass the best-configured metal-backed devices. Theoretical and experimental results all show that superior large-angle light scattering capability can be achieved by the diffuse medium reflectors, and the solar cell J-V enhancement is higher for solar cells using all-dielectric reflectors. Specifically, the measured diffused scattering efficiency (D.S.E.) of a diffuse medium reflector is >0.8 for the light trapping spectral range (600nm-1000nm), and the measured reflectance of a diffuse medium can be as high as silver if the geometry of embedded titanium oxide(TiO2) nanoparticles is optimized. Moreover, the diffuse medium reflectors have the additional advantage of room-temperature processing, low cost, and very high throughput. We believe that using all-dielectric solar cell reflectors is a way to approach the thermodynamic conversion limit by completely excluding metallic dissipation. (C) 2015 Optical Society of America
Low Cost All-Dielectric Thin-Film Solar Cell Using Diffuse Medium Reflectors
(2014)
Tseng, Chi Wei
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Fu, Sze Ming
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Lai, Shih-Yun
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Lai, Wei-Ming
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Yan, Sheng Lun
Diffuse reflectors can be beneficial for solar cells, due to no plasmonic loss, higher reflectance, decent light scattering, and low cost. Experimental and theoretical works are presented here to demonstrate its feasibility for photovoltaics.
The Coupled Electrical-Optical Simulation of Solar Cell J-V Degradation with Grating Heights
(2014)
Lin, Yu Chiun
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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
Solar cell with grating structure is used frequently for increased optical absorption, but it can lead to electrical degradation. Here coupled simulation is conducted to clarify the physical reason causing this J-V degradation.
The rigorous wave optics design of diffuse medium reflectors for photovoltaics
(2014-04-21)
Lin, Albert
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Fu, Sze Ming
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Zhong, Yan Kai
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Tseng, Chi Wei
;
Chen, Po Yu
Recently, diffuse reflectors are being incorporated into solar cells, due to the advantage of no metallic absorption loss, higher reflectance, decent light scattering property by embedded TiO2 scatterers, and the ease of fabrication. Different methods have been employed to analyze diffuse reflectors, including Monte Carlo method, N-flux method, and a one-dimensional approximation based on semi-coherent optics, and the calculated reflectance is around 80% by these methods. In this work, rigorous wave optics solution is used, and it is shown that the reflectance for diffuse medium mirrors can actually be as high as >99% over a broad spectral range, provided the TiO2 scatterer geometry is properly optimized. The bandwidth of diffuse reflectors is un-achievable by other dielectric mirrors such as distributed Bragg reflectors or high index contrast grating mirror, using the same index contrast. Finally, it is promisingly found that even if the distribution of TiO2 is random, the wide-band reflection can still be achieved for the optimized TiO2 geometry. Initial experimental result is included in the supplementary material which shows the high feasibility of diffuse medium mirrors for solar cells. (C) 2014 AIP Publishing LLC.