Browsing by Author "Chen, Po-Wei"

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Application of Porous a-Si:H Passivation Layer Deposited Using Si2H6 Precursor in Silicon Heterojunction Solar Cells
(2018-01-01)
Chen, Po-Wei
;
Chen, Pei-Ling
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Hsu, Hung-Jung
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Matsui, Takuya
;
Sai, Hitoshi
The improved silicon heterojunction solar cell efficiency by employing porous a-Si:H passivation layer deposited using Si2H6 precursor is presented. By introducing Si2H6 precursor into the commonly-used SiH4 plasma, it is demonstrated that the porosity of a-Si:H passivation layer can be increased significantly. A stack of the porous a-Si:H passivation layer with overlying dense a-Si:H capping layer preserves excellent interface passivation even after doped layer deposition. In the finished solar cell, improvements in Voc from 0.691 to 0.714 V and efficiency from 20.0 to 21.0% were obtained as a consequence of using porous a-Si:H passivation layer deposited under high Si2H6 concentration.
Asymmetric Coplanar Waveguide (ACPW) Zeroth-Order Resonant (ZOR) Antenna With High Efficiency and Bandwidth Enhancement
(2012)
Chen, Po-Wei
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Chen, Fu-Chiarng
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電機工程學系
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Department of Electrical and Computer Engineering
"A novel low-profile zeroth-order (ZOR) antenna is presented. The feature of ZOR based on periodic structures is employed to reduce the antenna size, while these antennas generally suffer from narrow bandwidth. A single-layer asymmetric coplanar waveguide (ACPW) structure is proposed to realize a bandwidth-extended ZOR antenna, where the antenna bandwidth is characterized by an equivalent circuit model. The ACPW-structure not only provides the design freedom, but also overcomes the design constraint of the traditional CPW. The ACPW ZOR antenna is verified by both full-wave simulations and experiments. As an advantage of the proposed method, the size of antenna is reduced, and the resonant frequency of zeroth-order mode is 1.94 GHz with radiation efficiency of 85%, measured 10-dB fractional bandwidth up to 10.3%, and omnidirectional peak gain of 2.3 dBi."
Development of Wider Bandgap n-type a-SiOx:H and mu c-SiOx:H as Both Doped and Intermediate Reflecting Layer for a-Si:H/a-Si1-xGex:H Tandem Solar Cells
(2016-07-01)
Chen, Po-Wei
;
Chen, Pei-Ling
;
Tsai, Chuang-Chuang
;
光電工程學系
;
Department of Photonics
In this work, we developed a-SiOx:H(n) and mu c-SiOx:H(n) films as n-type layer, intermediate reflecting layer (IRL), and back-reflecting layer (BRL) to improve the light management in silicon thin-film solar cells. In the development of SiOx:H films, by properly adjusting the oxygen content of the films, the optical bandgap of x-SiOx:H(n) can be increased while maintaining sufficient conductivity. Similar effect was found for a-SiOx:H(n). In a-Si:H single junction cells, employing a-SiOx:H(n) as the replacement for a-Si:H(n) resulted in a relative efficiency enhancement of 11.4% due to the reduced parasitic absorption loss. We have also found that pc-SiOx:H(n) can replace back ITO layer as BRL, leading to a relative efficiency gain of 7.6%. For a-Si:H/a-Sil..,Ge.,:H tandem cell, employing pf-SiOx:H(n) as IRL increased the current density of top cell. In addition, employing a-SiOx:H(n) as a replacement of a-Si:H(n) in the top cell increased the current density of bottom cell due to the reduction of absorption loss. Combining all the improvements, the a-Si:H/a-Si1-xGex:H tandem cell with efficiency of 9.2%, V-oc = 1.58 V, J(SC) = 8.43 mA/cm(2), and FF = 68.4% was obtained.
Development of Wider Bandgap n-type a-SiOx:H and mu c-SiOx:H as Both Doped and Intermediate Reflecting Layer for a-Si:H/a-Si1-xGex:H Tandem Solar Cells
(2016-07)
Chen, Po-Wei
;
Chen, Pei-Ling
;
Tsai, Chuang-Chuang
;
光電工程學系
;
Department of Photonics
In this work, we developed a-SiOx:H(n) and mu c-SiOx:H(n) films as n-type layer, intermediate reflecting layer (IRL), and back-reflecting layer (BRL) to improve the light management in silicon thin-film solar cells. In the development of SiOx:H films, by properly adjusting the oxygen content of the films, the optical bandgap of x-SiOx:H(n) can be increased while maintaining sufficient conductivity. Similar effect was found for a-SiOx:H(n). In a-Si:H single junction cells, employing a-SiOx:H(n) as the replacement for a-Si:H(n) resulted in a relative efficiency enhancement of 11.4% due to the reduced parasitic absorption loss. We have also found that pc-SiOx:H(n) can replace back ITO layer as BRL, leading to a relative efficiency gain of 7.6%. For a-Si:H/a-Sil..,Ge.,:H tandem cell, employing pf-SiOx:H(n) as IRL increased the current density of top cell. In addition, employing a-SiOx:H(n) as a replacement of a-Si:H(n) in the top cell increased the current density of bottom cell due to the reduction of absorption loss. Combining all the improvements, the a-Si:H/a-Si1-xGex:H tandem cell with efficiency of 9.2%, V-oc = 1.58 V, J(SC) = 8.43 mA/cm(2), and FF = 68.4% was obtained.
Impact of intrinsic amorphous silicon bilayers in silicon heterojunction solar cells
(2018-09-14)
Sai, Hitoshi
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Chen, Po-Wei
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Hsu, Hung-Jung
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Matsui, Takuya
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Nunomura, Shota
The impact of intrinsic amorphous silicon bilayers in amorphous silicon/crystalline silicon (a-Si:H/ c-Si) heterojunction solar cells is investigated. The microstructure factor R* of the interfacial a-Si: H layer, which is related to the Si-H bond microstructure and determined by infrared absorption spectroscopy, is controlled in a wide range by varying the growth pressure and the power density in plasma-enhanced chemical vapor deposition process. Surface passivation at the a-Si:H/c-Si interface is significantly improved by using an intrinsic a-Si:H bilayer, i.e., a stack of an interfacial layer with a large R* and an additional dense layer, particularly after the deposition of an overlying p-type a-Si:H layer. Consequently, the conversion efficiency of a-Si:H/c-Si heterojunction solar cells is markedly increased. However, it is also revealed that such an interfacial layer causes some negative effects including the increase in the series resistance and the current loss at the front side, depending on the growth condition. This result indicates that the interfacial layer has a significant impact on both the majority and the minority carrier transport. Thus, R* of the interfacial layer is an important parameter for obtaining good surface passivation at the a-Si/c-Si interface, but not the sole parameter determining the conversion efficiency of a-Si:H/c-Si heterojunction solar cells. Published by AIP Publishing.
Investigation of P-type Hydrogenated Nanocrystalline Silicon Grown by VHF-PECVD as Emitter in Silicon Heterojunction Solar Cells
(2018-01-01)
Chen, Pei-Ling
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Chen, Po-Wei
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Matsui, Takuya
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Sai, Hitoshi
;
Tsai, Chuang-Chuang
P-type hydrogenated nanocrystalline silicon (ncSi: H(p)) films as emitter layers in silicon heterojunction solar (SHJ) cells by VHF-PECVD (65 and 100 MHz) and standard RF-PECVD (13.56 MHz) were investigated. We demonstrate that the use of VHF-PECVD is advantageous in fast nucleation in a very thin layer (< 15 nm), which in turn results in improved TCO/p contact. In addition, the deposition of nc-Si: H (p) layer by VHF-PECVD can improve the surface passivation properties as evidenced by QSSPC lifetime measurement for the solar cell precursor (i. e., pi/ c-Si/ in). These results suggest that VHF plasma generates more atomic hydrogen flux, which brings beneficial aspects both in terms of nc-Si: H growth and post-hydrogenation. Compared to our standard a-Si: H(p) emitter, the use of nc-Si: H(p) prepared by 65 MHz PECVD improved the efficiency from 19.59% to 20.50%.
On the Variability of Threshold Voltage Window in Gate-Injection Versatile Memories with Sub-60mV/dec Subthreshold Swing and 10(12)-Cycling Endurance
(2016)
Chiu, Yu-Chien
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Chang, Chun-Yen
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Yen, Shiang-Shiou
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Fan, Chia-Chi
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Hsu, Hsiao-Hsuan
Incorporating a charge-trapped ZrSiO with ferroelectric HfZrO dielectrics, we demonstrated a gate-injection versatile memory with sub-60mV/dec subthreshold swing (SS) and large threshold voltage window (Delta V-T) of >2V under a fast 20-ns speed. Moreover, it is revealed that the local defects at ZrSiO/HfZrO interface affect the ferroelectric negative capacitance tuning and thus increases the variability of V-T and SS during 10(12) cycling endurance.
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%.
Study of Transition Region of p-Type SiOx:H as Window Layer in a-Si:H/a-S1-yGey:H Multijunction Solar Cells
(2016-01-01)
Chen, Pei-Ling
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Chen, Po-Wei
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Tsai, Chuang-Chuang
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光電工程學系
;
Department of Photonics
We have studied the p-type hydrogenated silicon oxide (SiOx:H) films prepared in the amorphous-to-microcrystalline transition region as a window layer in a-Si:H/a-S1-yGey:H multijunction solar cells. By increasing the H-2-to-SiH, flow ratio (R,) from 10 to 167, the SiOx:H(p) films remained amorphous and exhibited an increased hydrogen content from 10.2% to 12.2%. Compared to the amorphous SiOx:H(p) film prepared at low R-H2, the SiOx:H(p) film deposited at RH, of 167 exhibited a higher bandgap of 2.04 eV and a higher conductivity of 1.15 x 10(-5)S/cm. With the employment of SiOx:H(p) films prepared by increasing RH, from 10 to 167 in a-Si:H single-junction cell, the FF improved from 65% to 70% and the efficiency increased from 7.4% to 8.7%, owing to the enhanced optoelectrical properties of SiOx:H(p) and the improved p/i interface. However, the cell that employed Si0,:14(p) film with RH, over 175 degraded the p/i interface and degraded the cell performance, which were arising from the onset of crystallization in the window layer. Compared to the cell using standard a-SiC,:H(p), the a-Si:H/a-S1-yGey:H tandem cells employing SiOx:H(p) deposited with R-H2, of 167 showed an improved efficiency from 9.3% to 10.3%, with 17, of 1.60 V, J(sc) of 9.3 mA/cm(2), and FF of 68.9%.
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%.