Browsing by Author "Chou, Hao-Ming"

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A path-finding toward high-efficiency penternary Cu(In,Ga)(Se,S)(2) thin film solar module
(2019-01-01)
Huang, Chien-Yao
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Parashar, Parag
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Chou, Hao-Ming
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Lin, Yi-Shivan
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Lin, Albert
The optimal p-n junction structure in a state-of-the-art Cu(In,Ga)(Se,S)(2) thin-film solar module technology is investigated. For co-optimization design and path-finding, a TCAD model is developed with experimental samples. The engineerable parameters, i.e., F-Ga, GGI(avg), and CdS thickness, are demonstrated to play a critical role in determining the p-n junction properties such as dark current characteristics J(dark)(V), voltage-dependent photocurrent, localized carrier collection efficiency, and interface carrier transportation. We show the optimal Ga-grading is determined by a trade-off between the recombination loss in space charge region and the photo carrier collection in quasi-neutral region. The optimal CdS thickness is determined by a trade-off between carrier collection efficiency, short-circuit current (J(SC)) loss, and J(dark)(V), which depends on varied Ga-profiles. Overall, thin CdS (<= 10 nm) is preferred to reduce the J(SC) loss in accumulated Ga-profiles, while thicker CdS is preferred to enhance the carrier collection efficiency in flatter Ga-profiles. The band alignment effect on varied Cu(In,Ga)(Se,S)(2)/CdS junctions is also investigated. It is found sulfur-incorporation can suppress the V-OC saturation behavior at wide bandgap. For CIGSeS absorber with SS = 20% and D-p = 15%, the maximum V-OC of 780 mV can be achieved by co-optimized Ga-profile. Furthermore, varied Ga-profiles and CdS buffer layers are explored for pathfinding. An optimal p-n junction structure shows a relative + 40% efficiency improvement from 15.5% to 21.9%. This work shows the efficiency headroom of reported CIGSeS thin-film solar module technology through co-optimized CIGSeS composition gradient and buffer layer.
HIT Solar Cell Performance Enhancement with Luminescent Down Shifting Phenomenon
(2018-01-01)
Lin, Albert
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Huang, Chien-Yao
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Parashar, Parag
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Chou, Hao-Ming
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Lin, Yi-Shiuan
Luminescent down-shifting (LDS) phenomenon has been employed to enhance the HIT solar cell efficiency. The efficiency and J(SC) are increased by 2.3% and 11.5% respectively. External quantum efficiency (EQE) data supports our claim.
Performance comparison of III-V//Si and III-V//InGaAs multi-junction solar cells fabricated by the combination of mechanical stacking and wire bonding
(2019-03-13)
Kao, Yu-Cheng
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Chou, Hao-Ming
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Hsu, Shun-Chieh
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Lin, Albert
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Lin, Chien-Chung
The integration of III-V and Si multi-junction solar cells as photovoltaic devices has been studied in order to achieve high photovoltaic conversion efficiency. However, large differences in the coefficients of thermal expansion and the lattice parameters of GaAs, Si, and InGaAs have made it difficult to obtain high-efficiency solar cells grown as epilayers on Si and InP substrates. In this paper, two types of devices, including GaInP/GaAs stacked on Si (GalnP/GaAs//Si) and GaInP/GaAs stacked on InGaAs (GaInP/GaAs//InGaAs), are fabricated via mechanical stacking and wire bonding technologies. Mechanically stacked GaInP/GaAs//Si and GaInP/GaAsllInGaAs triple-junction solar cells are prepared via glue bonding. Current-voltage measurements of the two samples are made at room temperature. The short-circuit current densities of the GaInP/GaAs//Si and GaInP/GaAs//InGaAs solar cells are 13.37 and 13.66 mA/cm(2), while the open-circuit voltages of these two samples are measured to be 2.71 and 2.52V, respectively. After bonding the GaInP/GaAs dual-junction with the Si and InGaAs solar cells, the conversion efficiency is relatively improved by 32.6% and 30.9%, respectively, compared to the efficiency of the GaInP/GaAs dual-junction solar cell alone. This study demonstrates the high potential of combining mechanical stacked with wire bonding and ITO films to achieve high conversion efficiency in solar cells with three or more junctions.