High Efficiency Hydrogenated Nanocrystalline Silicon Solar Cells Deposited at High Rates

2010 ◽  
Vol 1245 ◽  
Author(s):  
Guozhen Yue ◽  
Laura Sivec ◽  
Baojie Yan ◽  
Jeff Yang ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Triple Junction ◽  
High Efficiency ◽  
Nanocrystalline Silicon ◽  
Active Area ◽  
Very High Frequency ◽  
Area Efficiency ◽  
Hydrogen Dilution ◽  
Back Reflectors ◽  
Junction Structure

AbstractWe report recent progress on hydrogenated nanocrystalline silicon (nc-Si:H) solar cells prepared at different deposition rates. The nc-Si:H intrinsic layer was deposited, using a modified very high frequency (MVHF) glow discharge technique, on Ag/ZnO back reflectors (BRs). The nc-Si:H material quality, especially the evolution of the nanocrystallites, was optimized using hydrogen dilution profiling. First, an initial active-area efficiency of 10.2% was achieved in a nc-Si:H single-junction cell deposited at ~5 Å/s. Using the improved nc-Si:H cell, we obtained 14.5% initial and 13.5% stable active-area efficiencies in an a-Si:H/nc-Si:H/nc-Si:H triple-junction structure. Second, we achieved a stabilized total-area efficiency of 12.5% using the same triple-junction structure but with nc-Si:H deposited at ~10 Å/s; the efficiency was measured at the National Renewable Energy Laboratory (NREL). Third, we developed a recipe using a shorter deposition time and obtained initial 13.0% and stable 12.7% active-area efficiencies for the same triple-junction design.

High efficiency amorphous and nanocrystalline silicon based multi-junction solar cells deposited at high rates on textured Ag/ZnO back reflectors

2009 ◽  
Vol 1153 ◽  
Author(s):  
Guozhen Yue ◽  
Laura Sivec ◽  
Baojie Yan ◽  
Jeff Yang ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Triple Junction ◽  
High Efficiency ◽  
Nanocrystalline Silicon ◽  
Open Circuit ◽  
Very High Frequency ◽  
Solar Cell Performance ◽  
Single Junction ◽  
Back Reflectors ◽  
Back Reflector

AbstractWe report our recent progress on nc-Si:H single-junction and a-Si:H/nc-Si:H/nc-Si:H triple-junction cells made by a modified very-high-frequency (MVHF) technique at deposition rates of 10-15 Å/s. First, we studied the effect of substrate texture on the nc-Si:H single-junction solar cell performance. We found that nc-Si:H single-junction cells made on bare stainless steel (SS) have a good fill factor (FF) of ˜0.73, while it decreased to ˜0.65 when the cells were deposited on textured Ag/ZnO back reflectors. The open-circuit voltage (Voc) also decreased. We used dark current-voltage (J-V), Raman, and X-ray diffraction (XRD) measurements to characterize the material properties. The dark J-V measurement showed that the reverse saturated current was increased by a factor of ˜30 when a textured Ag/ZnO back reflector was used. Raman results revealed that the nc-Si:H intrinsic layers in the two solar cells have similar crystallinity. However, they showed a different crystallographic orientation as indicated in XRD patterns. The material grown on Ag/ZnO has more random orientation than that on SS. These experimental results suggested that the deterioration of FF in nc-Si:H solar cells on textured Ag/ZnO was caused by poor nc-Si:H quality. Based on this study, we have improved our Ag/ZnO back reflector and the quality of nc-Si:H component cells and achieved an initial and stable active-area efficiencies of 13.4% and 12.1%, respectively, in an a-Si:H/nc-Si:H/nc-Si:H triple-junction cell.

Status of nc-Si:H Solar Cells at United Solar and Roadmap for Manufacturing a-Si:H and nc-Si:H Based Solar Panels

2007 ◽  
Vol 989 ◽  
Author(s):  
Baojie Yan ◽  
Guozhen Yue ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Triple Junction ◽  
Cell Structure ◽  
Nanocrystalline Silicon ◽  
Active Area ◽  
Solar Panels ◽  
Very High Frequency ◽  
Cell Efficiency ◽  
Critical Issues ◽  
Junction Structure

AbstractThis paper reviews the research and development of hydrogenated nanocrystalline silicon (nc-Si:H) solar cells at United Solar Ovonic LLC. We have been studying nc-Si:H solar cells since 2001 and have made significant progress. We have achieved an initial active-area cell efficiency of 15.1% using an a-Si:H/a-SiGe:H/nc-Si:H triple-junction structure, a stable active-area cell efficiency of 13.3% using an a-Si:H/nc-Si:H/nc-Si:H triple-junction structure, and a stable aperture-area (420 cm2) fully encapsulated module efficiency of 9.5% using an a-Si:H/nc-Si:H double-junction structure. Although the cell efficiencies with nc-Si:H in the middle and/or bottom cells have exceeded the corresponding efficiencies achieved using a-Si:H and a-SiGe:H, we still need to address several critical issues before using nc-Si:H in photovoltaic manufacturing plants. First, the cell efficiency needs to be improved further to show a clear advantage over the conventional a-Si:H/a-SiGe:H/a-SiGe:H triple-junction cell structure. Second, we need to increase the deposition rate further to make the nc-Si:H based technology more cost effective. Third, we need to develop a machine design to overcome the large-area uniformity issue, especially for very high frequency glow discharge deposition. Fourth, we need to qualify nc-Si:H based solar cell product, especially with respect to long term reliability. We have been addressing these critical issues, and will discuss the roadmap for manufacturing a-Si:H and nc-Si:H based solar panels using the roll-to-roll technology.

Microstructure Evolution with Thickness and Hydrogen Dilution Profile in Microcrystalline Silicon Solar Cells

2004 ◽  
Vol 808 ◽  
Author(s):  
Baojie Yan ◽  
Guozhen Yue ◽  
Jeffrey Yang ◽  
Subhendu Guha ◽  
D. L. Williamson ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Microstructure Evolution ◽  
Volume Fraction ◽  
Microcrystalline Silicon ◽  
Very High Frequency ◽  
Area Efficiency ◽  
Junction Solar Cell ◽  
Hydrogen Dilution ◽  
Back Reflectors

ABSTRACTHydrogenated microcrystalline silicon (m c-Si:H) solar cells with different thicknesses were deposited on specular stainless steel substrates and on textured Ag/ZnO back reflectors using RF and modified very high frequency glow discharge at various deposition rates. Raman spectra and X-ray diffraction patterns exhibit a significant increase of microcrystalline volume fraction and in grain size with film thickness. Atomic force microscopy reveals an increase in the size of microstructural features and the surface roughness with increasing thickness. Based on these results, we believe that the increase of the microcrystalline phase with thickness is the main reason for the deterioration of cell performance with the thickness of the intrinsic layer. To overcome this problem, we have developed a procedure of varying the hydrogen dilution ratio during deposition. Using this method, we have been successful in controlling the microstructure evolution and achieved an initial active-area efficiency of 8.4% for a c-Si:H single-junction solar cell, and 13.6% for an a-Si:H/a-SiGe:H/m c-Si:H triple-junction solar cell.

Hydrogenated Nanocrystalline Silicon based Solar Cell with 13.6% Stable Efficiency

2012 ◽  
Vol 1426 ◽  
pp. 33-38 ◽  
Author(s):  
Guozhen Yue ◽  
Baojie Yan ◽  
Laura Sivec ◽  
Tining Su ◽  
Yan Zhou ◽  
...  
Keyword(s):  
Solar Cells ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Nanocrystalline Silicon ◽  
Short Circuit Current Density ◽  
Buffer Layers ◽  
Very High Frequency ◽  
Hydrogen Dilution ◽  
Silicon Based ◽  
Junction Structure

ABSTRACTMulti-junction solar cells incorporating hydrogenated nanocrystalline silicon (nc-Si:H) exhibit a high current capability and low light-induced degradation. In this paper, we report our recent progress in developing nc-Si:H solar cells using a modified very-high-frequency glow discharge technique. We achieved a short-circuit current density >30 mA/cm2and 10.6% conversion efficiency from single-junction solar cells. Using the improved nc-Si:H cells in an a-Si:H/nc-Si:H/nc-Si:H triple-junction structure, we attained initial and stabilized efficiencies of 13.9% and 13.6%, respectively. Issues related to improving material properties and device structures are addressed. Besides using the conventional techniques, such as hydrogen dilution profiling, optimized Ag/ZnO back reflector, and buffer layers, we found that compensation from Boron and Oxygen micro-doping is also critical in obtaining the above achievements.

Microcrystalline Silicon Solar Cell Deposited Using Modified Very-High-Frequency Glow Discharge and Its Application in Multi-junction Structures

2004 ◽  
Vol 808 ◽  
Author(s):  
Guozhen Yue ◽  
Baojie Yan ◽  
Jessica M. Owens ◽  
Jeffrey Yang ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Glow Discharge ◽  
Triple Junction ◽  
High Frequency ◽  
Active Area ◽  
Microcrystalline Silicon ◽  
Very High Frequency ◽  
Bottom Cell ◽  
Junction Structure ◽  
Very High

ABSTRACTWe have used the modified very-high-frequency glow discharge technique to deposit hydrogenated microcrystalline silicon (m c-Si:H) solar cells at high rates for use as the bottom cell in a multi-junction structure. We have investigated c-Si:H single-junction, a-Si:H/ c-Si:H double-junction, and a-Si:H/a-SiGe:H/m c-Si:H triple-junction solar cells and achieved initial active area efficiencies of 7.7%, 12.5%, and 12.4%, respectively. Issues related to improving material properties and device structures are addressed. By taking advantage of a lower degradation in m c-Si:H than a-Si:H and a-SiGe:H alloys, we have minimized the light induced effect in multi-junction structures by designing a bottom-cell-limited current mismatching. As a result, we have obtained a stable active-area cell efficiency of 11.2% with an a-Si:H/a-SiGe:H/μ c-Si:H triple-junction structure.

scholarly journals Light trapping in hydrogenated amorphous and nano-crystalline silicon thin film solar cells

2009 ◽  
Vol 1153 ◽  
Author(s):  
Jeffrey Yang ◽  
Baojie Yan ◽  
Guozhen Yue ◽  
Subhendu Guha
Keyword(s):  
Stainless Steel ◽  
Solar Cells ◽  
Triple Junction ◽  
Crystalline Silicon ◽  
Light Trapping ◽  
Nano Crystalline ◽  
Back Reflectors ◽  
Back Reflector ◽  
Junction Structure ◽  
Hydrogenated Amorphous

AbstractLight trapping effect in hydrogenated amorphous silicon-germanium alloy (a-SiGe:H) and nano-crystalline silicon (nc-Si:H) thin film solar cells deposited on stainless steel substrates with various back reflectors is reviewed. Structural and optical properties of the Ag/ZnO back reflectors are systematically characterized and correlated to solar cell performance, especially the enhancement in photocurrent. The light trapping method used in our current production lines employing an a-Si:H/a-SiGe:H/a-SiGe:H triple-junction structure consists of a bi-layer of Al/ZnO back reflector with relatively thin Al and ZnO layers. Such Al/ZnO back reflectors enhance the short-circuit current density, Jsc, by ˜20% compared to bare stainless steel. In the laboratory, we use Ag/ZnO back reflector for higher Jsc and efficiency. The gain in Jsc is about ˜30% for an a-SiGe:H single-junction cell used in the bottom cell of a multi-junction structure. In recent years, we have also worked on the optimization of Ag/ZnO back reflectors for nano-crystalline silicon (nc-Si:H) solar cells. We have carried out a systematic study on the effect of texture for Ag and ZnO. We found that for a thin ZnO layer, a textured Ag layer is necessary to increase Jsc, even though the parasitic loss is higher at the Ag and ZnO interface due to the textured Ag. However, a flat Ag can be used for a thick ZnO to reduce the parasitic loss, while the light scattering is provided by the textured ZnO. The gain in Jsc for nc-Si:H solar cells on Ag/ZnO back reflectors is in the range of ˜60-75% compared to cells deposited on bare stainless steel, which is much larger than the enhancement observed for a-SiGe:H cells. The highest total current density achieved in an a-Si:H/a-SiGe:H/nc-Si:H triple-junction structure on Ag/ZnO back reflector is 28.6 mA/cm2, while it is 26.9 mA/cm2 for a high efficiency a-Si:H/a-SiGe:H/a-SiGe:H triple-junction cell.

Amorphous Silicon Alloy Materials and Solar Cells Near the Threshold of Microcrystallinity

1999 ◽  
Vol 557 ◽  
Author(s):  
J. Yang ◽  
S. Guha
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
Triple Junction ◽  
High Efficiency ◽  
Spectral Response ◽  
High Quality ◽  
Silicon Alloys ◽  
Solar Cell Performance ◽  
Hydrogen Dilution

AbstractOne of the most effective techniques used to obtain high quality amorphous silicon alloys is the use of hydrogen dilution during film growth. The resultant material exhibits a more ordered microstructure and gives rise to high efficiency solar cells. As the hydrogen dilution increases, however, a threshold is reached, beyond which microcrystallites begin to form rapidly. In this paper, we review some of the interesting features associated with the thin film materials obtained from various hydrogen dilutions. They include the observation of linear-like objects in the TEM micrograph, a shift of the principal Si TO band in the Raman spectrum, a sharp, low temperature peak in the H2 evolution spectrum, a shift of the wagging mode in the IR spectrum, and a narrowing of the Si (111) peak in the X-ray diffraction pattern. These spectroscopic tools have allowed us to optimize deposition conditions to near the threshold of microcrystallinity and obtain desired high quality materials. Incorporation of the improved materials into device configuration has significantly enhanced the solar cell performance. Using a spectral-splitting, triple-junction configuration, the spectral response of a typical high efficiency device spans from below 350 nm to beyond 950 nm with a peak quantum efficiency exceeding 90%; the triple stack generates a photocurrent of 27 mA/cm2. This paper describes the effect of the improved materials on various solar cell structures, including a 13% active-area, stable triple-junction device.

11.0% Stable Efficiency on Large Area, Encapsulated a-Si:H and a-SiGe:H based Multijunction Solar Cells Using HF Technology

2011 ◽  
Vol 1321 ◽  
Author(s):  
A. Banerjee ◽  
D. Beglau ◽  
T. Su ◽  
G. Pietka ◽  
G. Yue ◽  
...  
Keyword(s):  
Solar Cells ◽  
Triple Junction ◽  
Gas Flow ◽  
High Efficiency ◽  
Open Circuit ◽  
Large Area ◽  
Multijunction Solar Cells ◽  
Double Junction ◽  
Junction Structure ◽  
Cell Thickness

ABSTRACTWe report on the investigation of large area a-Si:H/a-SiGe:H double-junction and a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cells prepared by our proprietary High Frequency (HF) glow discharge technique. For investigative purposes, we initially used the simpler double-junction structure. We studied the effect of: (1) Ge content, (2) cell thickness, and (3) SiH4 and GeH4 gas flow on the light-induced degradation of the solar cells. Our results show that the double-junction cells with different Ge concentration have open-circuit voltage (Voc) in the range of 1.62-1.75 V. Voc exhibits a flat plateau in the range of 1.65-1.72 V for both initial and stabilized states. The light-induced degradation for cells in this range of Voc is insensitive to the Ge content. In terms of thickness dependence of the intrinsic layers, we found that the initial efficiency increases with cell thickness in the thickness range 2000-4000 Å. However, light-induced degradation increases with increasing thickness. Consequently, the stabilized efficiency is invariant with cell thickness in the thickness range studied. The results of SiH4 and GeH4 gas flow on cell characteristics demonstrate that the deposition rate decreases by only 20% when the active gas flow is reduced to 0.25 times standard flow. The initial and stabilized efficiencies are similar. The information gleaned from the study was used to fabricate high efficiency, large area (~464 cm2) double- and triple-junction solar cells. The highest stable efficiency, as measured by NREL, was 9.8% and 11.0% for the double- and triple-junction structures, respectively.

Amorphous Silicon Alloy Solar Cells Near the Threshold of Amorphous-to-Microcrystalline Transition

2000 ◽  
Vol 609 ◽  
Author(s):  
Jeffrey Yang ◽  
Kenneth Lord ◽  
Subhendu Guha ◽  
S.R. Ovshinsky
Keyword(s):  
Solar Cells ◽  
Amorphous Silicon ◽  
High Efficiency ◽  
Open Circuit Voltage ◽  
Open Circuit ◽  
Area Efficiency ◽  
Junction Device ◽  
Tandem Structure ◽  
Double Junction ◽  
Junction Structure

ABSTRACTA systematic study has been made of amorphous silicon (a-Si) alloy solar cells using various hydrogen dilutions during the growth of the intrinsic (i) layer. We find that the open-circuit voltage (Voc) of the cells increases as the dilution increases; it then reaches a maximum before it decreases dramatically. This sudden drop in Voc is attributed to the transition from amorphous silicon to microcrystalline inclusions in the i layer. We study i-layer thicknesses ranging from 1000 Å to 5000 Å and find that the transition occurs in all thicknesses investigated. Based on this study, a-Si alloy p i n solar cells suitable for use in the top cell of a high efficiency triple-junction structure are made. By selecting an appropriate dilution, cells with Voc greater than 1 V can be achieved readily. Solar cells made near the threshold not only exhibit higher initial characteristics but also better stability against light soaking. We have compared top cells made near the threshold with our previous best data, and found that both the initial and stable efficiencies are superior for the near-threshold cells. For an a-Si/a-Si double-junction device, a Voc value exceeding 2 V has been obtained using thin component cells. Thicker component cells give rise to an initial active-area efficiency of 11.9% for this tandem structure.

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