Browsing by Author "Hsu, Cheng-Hang"

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Applications of mu c-SiOx:H as integrated n-layer and back transparent conductive oxide for a-Si:H/mu c-Si:H tandem cells
(2014-05-01)
Liang, Shin-Wei
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Huang, Yen-Tang
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Hsu, Hung-Jung
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Hsu, Cheng-Hang
;
Tsai, Chuang-Chuang
We have prepared n-type hydrogenated microcrystalline silicon oxide [mu c-SiOx:H(n)] films with oxygen contents from 0 to 37.3 at. % by varying the CO2-to-SiH4 flow ratio in a plasma-enhanced chemical vapor deposition (PECVD) system. By using mu c-SiOx:H(n) as an effective replacement for integrated mu c-Si:H(n) and indium-tin oxide (ITO), mu c-Si:H single-junction and a-Si:H/mu c-Si:H tandem cells exhibited significantly improved efficiencies of 6.35 and 10.53%, respectively. The improvement of the single-junction and tandem cells mainly arose from the enhancement of long-wavelength optical absorption in mu c-Si:H absorbers, which was confirmed by a quantum efficiency instrument showing a markedly enhanced spectral response at wavelengths from 600 to 1100 nm. Moreover, all the PECVD processes, except the metal contact, had an advantage of in situ deposition without breaking vacuum, thereby minimizing contamination of the interface. The simplified cell fabrication can enhance the fill factor, which will benefit industrial production. (C) 2014 The Japan Society of Applied Physics
Development of Hydrogenated Microcrystalline Silicon-Germanium Alloys for Improving Long-Wavelength Absorption in Si-Based Thin-Film Solar Cells
(2014)
Huang, Yen-Tang
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Hsu, Hung-Jung
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Liang, Shin-Wei
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Hsu, Cheng-Hang
;
Tsai, Chuang-Chuang
Hydrogenated microcrystalline silicon-germanium (mu c-Si1-xGex:H) alloys were developed for application in Si-based thin-film solar cells. The effects of the germane concentration (R-GeH4) and the hydrogen ratio (R-H2) on the mu c-Si1-xGex:H alloys and the corresponding single-junction thin-film solar cells were studied. The behaviors of Ge incorporation in a-Si1-xGex:H and mu c-Si1-xGex:H were also compared. Similar to a-Si1-xGex:H, the preferential Ge incorporation was observed in mu c-Si1-xGex:H. Moreover, a higher R-H2 significantly promoted Ge incorporation for a-Si1-xGex: H, while the Ge content was not affected by R-H2 in mu c-Si1-xGex:H growth. Furthermore, to eliminate the crystallization effect, the 0.9 mu m thick absorbers with a similar crystalline volume fraction were applied. With the increasing R-GeH4, the accompanied increase in Ge content of mu c-Si1-xGex:H narrowed the bandgap and markedly enhanced the long-wavelength absorption. However, the bias-dependent EQE measurement revealed that too much Ge incorporation in absorber deteriorated carrier collection and cell performance. With the optimization of R-H2 and R-GeH4, the single-junction mu c-Si1-xGex:H cell achieved an efficiency of 5.48%, corresponding to the crystalline volume fraction of 50.5% and Ge content of 13.2 at.%. Compared to mu c-Si:H cell, the external quantum efficiency at 800nm had a relative increase by 33.1%.
Development of plasma-enhanced chemical vapor deposition microcrystalline silicon oxide as a replacement for N-type or back transparent conducting oxide layers in amorphous silicon single-junction solar cells
(2014-07-01)
Liang, Shin-Wei
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Hsu, Hung-Jung
;
Hsu, Cheng-Hang
;
Tsai, Chuang-Chuang
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光電工程學系
The n-type hydrogenated microcrystalline silicon oxide (mu c-SiOx:H(n)) thin films with varied electrical and optical properties were prepared. We employed mu c-SiOx:H(n) as a replacement for n-type hydrogenated amorphous silicon (a-Si: H(n)) or back transparent conducting oxide (TCO) layers in hydrogenated amorphous silicon (a-Si:H) single-junction solar cells. Compared to the standard cell with a-Si:H(n)/ITO/Ag back reflecting structure, the cell using a-Si: H(n)/mu c-SiOx:H(n)/Ag or mu c-SiOx:H(n)/Ag showed a similar or even better performance. This improvement of cell performance mainly arose from the increased short-circuit current density (J(SC)) that originated from the increased long wavelength (580-660 nm) absorption in the absorber confirmed by the quantum efficiency measurement. The "all plasma-enhanced chemical vapor deposition" (if the front TCO and metal contact are disregarded) process without TCO (indium tin oxide, ITO) sputtering can simplify the fabrication and result in better interface quality. Compared to the standard cell, the conversion efficiency of a-Si:H cells using an 80 nm thick mu c-SiOx:H(n)/Ag back reflecting structure was enhanced from 9.32% to 9.84%, with V-OC = 0.90 V, J(SC) = 14.84 mA/cm(2), and FF = 73.7%.
Effect of TCO/mu c-Si:H Interface Modification on Hydrogenated Microcrystalline Silicon Thin-Film Solar Cells
(2013)
Liang, Shin-Wei
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Hsu, Cheng-Hang
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Tsai, Chuang-Chuang
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光電工程學系
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Department of Photonics
The effects of H-2 plasma exposure on optical, electrical, and structural properties of fluorine-doped tin oxide (FTO) and AZO/FTO substrates have been investigated. With increasing the time of H-2-plasma exposure, the hydrogen radical and ions penetrated through the FTO surface to form more suboxides such as SnO and metallic Sn, which was confirmed by the XPS analysis. The Sn reduction on the FTO surface can be effectively eliminated by capping the FTO with a very thin layer of sputtered aluminum-doped zinc oxide (AZO), as confirmed by the XPS analysis. By using the AZO/FTO as front TCO with the subsequent annealing, the p-i-n mu c-Si:H cell exhibited a significantly enhanced JSC from 15.97 to 19.40 mA/cm(2) and an increased conversion efficiency from 5.69% to 7.09%. This significant enhancement was ascribed to the effective elimination of the Sn reduction on the FTO surface by the thin AZO layer during the Si-based thin-film deposition with hydrogen-rich plasma exposure. Moreover, the subsequent annealing of the sputtered AZO could lead to less defects as well as a better interface of AZO/FTO.
Enhancement of Spectral Response in mu c-Si1-xGex:H Thin-Film Solar Cells with a-Si:H/mu c-Si:H P-Type Window Layers
(2015-01-01)
Huang, Yen-Tang
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Hsu, Cheng-Hang
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Tsai, Chuang-Chuang
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光電工程學系
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光電工程研究所
The hydrogenated amorphous silicon (a-Si:H)/hydrogenated microcrystalline silicon (mu c-Si:H) double p-type window layer has been developed and applied for improving microcrystalline silicon-germanium p-i-n single-junction thin-film solar cells deposited on textured SnO2:F-coated glass substrates. The substrates of SnO2:F, SnO2:F/mu c-Si:H(p), and SnO2:F/a-Si: H(p) were exposed to H-2 plasma to investigate the property change. Our results showed that capping a thin layer of a-Si: H(p) on SnO2:F can minimize the Sn reduction during the deposition process which had H-2-containing plasma. Optical measurement has also revealed that a-Si: H(p) capped SnO2:F glass had a higher optical transmittance. When the 20 nm mu c-Si: H(p) layer was replaced by a 3 nm a-Si: H(p)/17 nm mu c-Si:H(p) double window layer in the cell, the conversion efficiency (eta) and the short-circuit current density (J(SC)) were increased by 16.6% and 16.4%, respectively. Compared to the standard cell with the 20 nm mu c-Si:H(p) window layer, an improved conversion efficiency of 6.19% can be obtained for the cell having a-Si:H(p)/mu c-Si: H(p) window layer, with V-OC = 490 mV, J(SC) = 19.50 mA/cm(2), and FF = 64.83%.
Improved light management in a-Si:H/a-Si1-xGex:H tandem cells by employing multi-functional n-type microcrystalline silicon oxide
(2014-05-01)
Hsu, Hung-Jung
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Liang, Shin-Wei
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Huang, Yen-Tang
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Hsu, Cheng-Hang
;
Tsai, Chuang-Chuang
In this work, the development of plasma-enhanced chemical vapor deposition (PECVD) mu c-SiOx:H(n) and its application to a-Si:H/a-Si1-xGex:H tandem cells as the intermediate reflecting layer (IRL) and back reflector (BR) is presented. The n-type microcrystalline silicon oxide [mu c-SiOx:H(n)] was used as multifunctional layers in silicon thin-film solar cells owing to its wide bandgap and low refractive index. In the development of mu c-SiOx:H(n), increasing RF power increased film oxygen content, which widened the bandgap while reducing dark conductivity. Applying the mu c-SiOx:H to a-Si:H/a-Si1-xGex:H tandem cells as IRL and BR significantly improved cell performance. The mu c-SiOx:H(n) IRL increases the current of the top cell, thus improving the light management in a-Si:H/a-Si1-xGex:H tandem cells. On the other hand, the mu c-SiOx:H(n) can be used as the BR replacing the n-type a-Si:H and ITO layers. The mu c-SiOx:H increased cell conversion efficiency by 12.9% as IRL, and by 9.7% as BR, achieving 10.03% efficiency. (C) 2014 The Japan Society of Applied Physics
Improvement of a-Si1-xGex:H single-junction thin-film solar cell performance by bandgap profiling techniques
(2012-09-01)
Hsu, Hung-Jung
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Hsu, Cheng-Hang
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Tsai, Chuang-Chuang
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資訊工程學系
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Department of Computer Science
In this work, the effect of hydrogen dilution on the Ge content of the film and the effect of bandgap grading in the a-S1-xGex:H absorber near the p/i and the i/n interfaces on cell performance were discussed. The a-Si1-xGex:H single-junction solar cells were improved by employing both p/i grading and i/n grading. The i/n grading increased the V-OC and the FF while it also reduced the J(SC) as compared to the cell without grading. Presumably the potential gradient established by the i/n grading facilitates the hole transport hereby improved by the FF. On the contrary, the potential barrier established by the p/i grading seemed to limit the cell performance and constrain the p/i grading width below 20 nm due to the drop in FF and J(SC). Combining the effects of bandgap grading on the V-OC, J(SC) and FF, the suitable thicknesses of the p/i and the i/n grading were 20 nm and 45 nm, respectively. Finally, the grading structures accompanied with further optimization in doped layers were integrated to achieve a cell efficiency of 8.59%. (C) 2012 Elsevier B.V. All rights reserved.
Optimization of a-Si1-xGex:H single-junction and a-Si:H/a-Si1-xGex:H tandem solar cells with enhanced optical management
(2014-07-01)
Hsu, Hung-Jung
;
Liang, Shin-Wei
;
Hsu, Cheng-Hang
;
Tsai, Chuang-Chuang
;
光電工程學系
This work aimed at improving the optical management of a-Si: H/a-Si1-xGex:H tandem cells and a-Si1-xGex:H single-junction cells. To improve the optical management, the effects of the a-Si1-xGex:H bandgap, the bandgap graded absorber and the n-type mu c-SiOx:H back reflecting layer on the cell performance were investigated. Optical reflection spectra, internal quantum efficiency, external quantum efficiency (EQE), and cell performance were used to evaluate the improvement of the optical properties of solar cells. The tandem cells with a-Si1-xGex:H bandgap of 1.53 eV exhibited sufficient optical absorption from 630 to 900 nm and thus lead to higher J(SC). Second, the EQE of a-Si1-xGex:H single-junction cell was significantly enhanced from 630 to 720 nm by employing bandgap graded absorber that relatively improved the J(SC) by 3.8% despite that the reduction in EQE from 720 to 900 nm compared to the cell without bandgap grading. Moreover, the mu c-SiOx:H(n)/Ag back reflector showed higher optical reflection than a-Si:H(n)/Ag did, which relatively improved the J(SC) by 12.3%. The cell with mu c-SiOx:H(n)/Ag back reflector exhibited a comparable J(SC) and efficiency to the cell with ITO-Ag. The previously mentioned approaches are relevant to enhance the optical management in cells and can be applied to silicon-based thin-film solar cells.
Optimization of mu c-Si1-xGex:H Single-Junction Solar Cells with Enhanced Spectral Response and Improved Film Quality
(2015-01-01)
Huang, Yen-Tang
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Chen, Pei-Ling
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Chen, Po-Wei
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Hsu, Hung-Jung
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Hsu, Cheng-Hang
Effects of RF power on optical, electrical, and structural properties of mu c-Si1-xGex:H films was reported. Raman and FTIR spectra from mu c-Si1-xGex:H films reflected the variation in microstructure and bonding configuration. Unlike increasing the germane concentration for Ge incorporation, low RF power enhanced Ge incorporation efficiency in mu c-Si1-xGex:H alloy. By decreasing RF power from 100 to 50 W at a fixed reactant gas ratio, the optical bandgap of mu c-Si1-xGex:H was reduced owing to the increase in Ge content from 11.2 to 23.8 at.%, while Ge-related defects and amorphous phase were increased. Consequently, photo conductivity of 1.62 x 10(-5) S/cm was obtained for the mu c-Si1-xGex:H film deposited at 60 W. By applying 0.9 mu m thick mu c-Si1-xGex:H absorber with X-C of 48% and [Ge] of 16.4 at.% in the single-junction cell, efficiency of 6.18% was obtained. The long-wavelength response of mu c-Si1-xGex:H cell was significantly enhanced compared with the mu c-Si:H cell. In the case of tandem cells, 0.24 mu m a-Si:H/0.9 mu m mu c-Si1-xGex:H tandem cell exhibited a comparable spectral response as 0.24 mu m a-Si:H/1.4 mu m mu c-Si:H tandem cell and achieved an efficiency of 9.44%.
Structural evolution of silicon oxide nanowires via head-growth solid-liquid-solid process
(2007-11-01)
Hsu, Cheng-Hang
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Chan, Shih-Yu
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Chen, Chia-Fu
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材料科學與工程學系
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Department of Materials Science and Engineering
In this paper, we propose a growth mechanism for silicon oxide nanowires (SiONWs) as a unique solid-liquid-solid process. SiONWs were synthesized in a furnace at 1000 degrees C and cooled at a high rate. Nickel and gold were introduced as catalysts to dissolve and precipitate the silicon oxide originally prepared by wet oxidation. The ratio of nickel to gold determined the precipitation rate and different "octopus-like" structures were formed. At a specific cooling rate, composition and amount of a catalyst, aligned silicon oxide nanowires with unattached ends were obtained.
The Effect of Bandgap Graded Absorber on the Performance of a-Si1-xGex: H Single-Junction Cells with mu c-SiOx:H N-Type Layer
(2013)
Hsu, Hung-Jung
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Hsu, Cheng-Hang
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Tsai, Chuang-Chuang
;
光電工程學系
;
Department of Photonics
We reported the effect of bandgap grading of absorbers on the performance of a-Si1-xGex:H cells employing mu c-SiOx:H n-layer. The influence of bandgap grading widths extended from the p-layer (the p/i grading) and the n-layer (the i/n grading) to the absorber on the cell performance which were systematically studied. The p/i grading reduced the interface defects and thus improved the v(OC). The reduced J(SC) and FF were presumably due to the degraded hole transport by the potential gradient of p/i grading. Increasing the i/n grading width improved the carrier collection significantly. The EQE, the J(SC), and the FF were improved substantially. Bias-dependent EQE revealed that the carrier collection is efficient in the cell employing optimal i/n grading. On the other hand, increasing the i/n grading width was accompanied by the decrease in long-wavelength response which potentially constrained the i/n grading width. Compared to the cell without grading, the a-Si1-xGex:H cells with optimal p/i and i/n grading width improved the efficiency from 5.5 to 7.5%.
Wide-Range Enhancement of Spectral Response by Highly Conductive and Transparent mu c-SiOx:H Doped Layers in mu c-Si:H and a-Si:H/mu c-Si:H Thin-Film Solar Cells
(2016-01-01)
Chen, Pei-Ling
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Chen, Po-Wei
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Hsiao, Min-Wen
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Hsu, Cheng-Hang
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Tsai, Chuang-Chuang
Theenhancement of optical absorption of silicon thin-film solar cells by the p-and n-type mu c-SiOx:H as doped and functional layers was presented. The effects of deposition conditions and oxygen content on optical, electrical, and structural properties of mu c-SiOx:H films were also discussed. Regarding the doped mu c-SiOx:H films, the wide optical band gap (E-04) of 2.33 eV while maintaining a high conductivity of 0.2 S/cm could be obtained with oxygen incorporation of 20 at.%. Compared to the conventional mu c-Si:H(p) as window layer in mu c-Si:H single-junction solar cells, the application of mu c-SiOx:H(p) increased the V-OC and led to a significant enhancement in the short-wavelength spectral response. Meanwhile, the employment of mu c-SiOx:H(n) instead of conventional ITO as back reflecting layer (BRL) enhanced the external quantum efficiency (EQE) of mu c-Si:H single-junction cell in the long-wavelength region, leading to a relative efficiency gain of 10%. Compared to the reference cell, the optimized a-Si:H/mu c-Si:H tandem cell by applying p-and n-type mu c-SiOx:H films achieved a V-OC of 1.37V, J(SC) of 10.55 mA/cm(2), FF of 73.67%, and efficiency of 10.51%, which was a relative enhancement of 16%.