Advanced Deposition Phase Diagrams for Guiding Si:H-Based Multijunction Solar Cells

2007 ◽  
Vol 989 ◽  
Author(s):  
Jason Collins ◽  
Nikolas J. Podraza ◽  
Jian Li ◽  
Xinmin Cao ◽  
Xunming Deng ◽  
...  
Keyword(s):  
Solar Cells ◽  
Phase Diagrams ◽  
Silicon Germanium ◽  
Chemical Vapor ◽  
Very High Frequency ◽  
Hydrogenated Silicon ◽  
Si Substrates ◽  
Cell Structures ◽  
Multijunction Solar Cells ◽  
Back Reflectors

AbstractPhase diagrams have been established to describe very high frequency (vhf) plasma-enhanced chemical vapor deposition (PECVD) processes for intrinsic hydrogenated silicon (Si:H) and silicon-germanium alloy (Si1-xGex:H) thin films using crystalline Si substrates that have been over-deposited with n-type amorphous Si:H (a-Si:H). The Si:H and Si1-xGex:H processes are applied for the top and middle i-layers of triple-junction a-Si:H-based n-i-p solar cells fabricated at University of Toledo. Identical n/i cell structures were co-deposited on textured Ag/ZnO back-reflectors in order to correlate the phase diagram and the performance of single-junction solar cells, the latter completed through over-deposition of the p-layer and top contact. This study has reaffirmed that the highest efficiencies for a-Si:H and a-Si1-xGex:H solar cells are obtained when the i-layers are prepared under maximal H2 dilution conditions.

INVESTIGATION OF THE Si:H FILMS DEPOSITED NEAR THE TRANSITION REGION FOR APPLICATION IN SOLAR CELLS

2006 ◽  
Vol 20 (27) ◽  
pp. 1739-1747 ◽  
Author(s):  
QINGSONG LEI ◽  
ZHIMENG WU ◽  
XINHUA GENG ◽  
YING ZHAO ◽  
JIANPING XI
Keyword(s):  
Thin Films ◽  
Solar Cells ◽  
Transition Region ◽  
Chemical Vapor ◽  
Transition Process ◽  
Very High Frequency ◽  
Working Pressure ◽  
Hydrogenated Silicon ◽  
Silicon Thin Films ◽  
Narrow Region

Hydrogenated silicon thin films (Si:H) have been deposited by using very high-frequency plasma-enhanced chemical vapor deposition (VHF PECVD). The structural, electrical and optical properties of the films were characterized. The transition process and the effect of pressure were studied. Results suggest that a narrow region, in which the transition from microcrystalline to amorphous growth takes place, exists in the regime of silane concentration (SC). This region is influenced by the working pressure (P). At lower pressure, the transition region is shifted to higher SC. Microcrystalline silicon (μ c-Si:H ) thin films deposited near transition region was applied as i-layer to the p-i-n solar cells. An efficiency of about 5.30% was obtained.

scholarly journals High Quality Amorphous Silicon Germanium Alloy Solar Cells Made by Hot-wire CVD at 10 Å/s

2001 ◽  
Vol 664 ◽  
Author(s):  
Qi Wang ◽  
Eugene Iwaniczko ◽  
Jeffrey Yang ◽  
Kenneth Lord ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Amorphous Silicon ◽  
Silicon Germanium ◽  
Chemical Vapor ◽  
Hot Wire ◽  
High Quality ◽  
Area Efficiency ◽  
Back Reflectors ◽  
Double Junction ◽  
Amorphous Silicon Germanium

ABSTRACTHigh quality amorphous silicon germanium (a-SiGe:H) alloys have been obtained using the hot wire chemical vapor deposition (HWCVD) from a gas mixture of SiH4, GeH4, and H2 at a deposition rate of ∼10 Å/s. Solar cells in a SS/n-i-p/ITO configuration are evaluated in which the n- and i-layers are deposited by HWCVD at NREL and the microcrystalline p-layer by conventional RF glow discharge in a separate reactor by United Solar. Effects of hydrogen dilution and step-wise bandgap profile have been studied and optimized. The best cell has an average optical bandgap of 1.6 eV and incorporates multi-bandgap steps where the narrow-most bandgap is near the p-i interface. J-V characteristics are measured under AM 1.5 illumination with a λ>530 nm filter. The best initial power output obtained exceeds 4 mW/cm2, which is usually used as an indicator for a good quality middle-gap cell. Double-junction cells are made on textured Ag/ZnO back reflectors. The bottom cell uses the optimized a-SiGe:H alloy cell by HWCVD, and the top cell uses an optimized a-Si:H cell near the amorphous-to-microcrystalline transition by PECVD at ∼1 Å/s. The best double-junction cell made to date exhibits an initial AM 1.5 active-area efficiency of 11.7%, and a stable efficiency after 1000 hours of one sun light soaking of 9.6%.

Hydrogenated Microcrystalline Silicon Single-Junction and Multi-Junction Solar Cells

2003 ◽  
Vol 762 ◽  
Author(s):  
Baojie Yan ◽  
Guozhen Yue ◽  
Jeffrey Yang ◽  
Arindam Banerjee ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Glow Discharge ◽  
Silicon Germanium ◽  
Active Area ◽  
Microcrystalline Silicon ◽  
Very High Frequency ◽  
Hydrogenated Silicon ◽  
Area Efficiency ◽  
Bottom Cell

AbstractThis paper summarizes our recent studies of hydrogenated microcrystalline silicon (μc-Si:H) solar cells as a potential substitute for hydrogenated silicon germanium alloy (a-SiGe:H) bottom cells in multi-junction structures. Conventional radio frequency (RF) glow discharge is used to deposit hydrogenated amorphous silicon (a-Si:H) and μc-Si:H at low rates (∼ 1 Å/s), searching for the highest efficiency. We have achieved an initial active-area efficiency of 13.0% and stable efficiency of 11.2% using an a-Si:H/μc-Si:H double-junction structure. Modified very high frequency (MVHF) glow discharge is used to deposit a-Si:H and μc-Si:H at high rates (∼ 3-10 Å/s) for comparison with our a-Si:H/a-SiGe:H/a-SiGe:H triple-junction production technology. The deposition time for the μc-Si:H intrinsic (i) layer in the bottom cell should be less than 30 minutes in order to be acceptable for mass production. To date, an initial active-area efficiency of 12.3% has been achieved with the bottom cell deposited in 50 minutes. By increasing the deposition rate and reducing the bottom cell thickness, we have achieved an initial active-area efficiency of 11.4% with the bottom cellilayer deposited in 30 minutes. The cell stabilized to 10.4% after prolonged light soaking. We will address issues related to μc-Si:H material, solar cell design, solar cell analysis, and stability.

Development of Deposition Phase Diagrams for Thin Film Si:H and Si1-xGex:H Using Real Time Spectroscopic Ellipsometry

2005 ◽  
Vol 862 ◽  
Author(s):  
N. J. Podraza ◽  
G. M. Ferreira ◽  
C. R. Wronski ◽  
R. W. Collins
Keyword(s):  
Phase Diagram ◽  
Phase Diagrams ◽  
Real Time ◽  
Spectroscopic Ellipsometry ◽  
Silicon Germanium ◽  
Crystalline Silicon ◽  
Thick Layer ◽  
Chemical Vapor ◽  
Surface Stability ◽  
Si Substrates

AbstractThe growth of hydrogenated silicon (Si:H) and silicon-germanium alloys (Si1-xGex:H) by plasma-enhanced chemical vapor deposition (PECVD) on crystalline silicon (c-Si) substrates has been studied by real time spectroscopic ellipsometry (RTSE). The motivation is to develop deposition phase diagrams that can provide greater insight into the optimization of amorphous Si1-xGex:H (a-Si1-xGex:H) for multijunction photovoltaics. In initial studies, the phase diagram for bottom cell a-Si1-xGex:H (Eg ˜ 1.4 eV) is found to exhibit fundamental similarities to that for Si:H when both materials are prepared under standard PECVD conditions that optimize pure a-Si:H. These similarities suggest directions for optimizing a-Si1-xGex:H by identifying conditions under which a smooth, stable surface is obtained to the largest possible bulk layer thickness. In phase diagram development for PECVD Si1-xGex:H on c-Si, it has been found that the highest surface stability and smoothest surfaces are obtained using cathodic deposition (self bias: ˜-20 V) with a H2-dilution level just below that of the amorphous-to-(mixed-phase microcrystalline) [→(a+μc)] transition for a thick layer. Due to the promising nature of these results, full phase diagrams are compared for cathodic and anodic Si1-xGex:H as well as for cathodic and anodic Si:H, all on c-Si substrates. The cathodic phase diagram for Si1-xGex:H reveals a narrow range of significant improvement in surface structural evolution near the →(a+μc) transition, and for a-Si:H reveals an extension of the ultrasmooth protocrystalline regime to a much wider range of thickness.

scholarly journals Growth of GaP Layers on Si Substrates in a Standard MOVPE Reactor for Multijunction Solar Cells

Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 398
Author(s):  
Pablo Caño ◽  
Carmen M. Ruiz ◽  
Amalia Navarro ◽  
Beatriz Galiana ◽  
Iván García ◽  
...  
Keyword(s):  
Solar Cells ◽  
Gallium Phosphide ◽  
Growth Process ◽  
Electrical Characterization ◽  
Substrate Preparation ◽  
Nucleation Layer ◽  
Si Substrates ◽  
Ideal Candidate ◽  
Multijunction Solar Cells ◽  
Multijunction Solar Cell

Gallium phosphide (GaP) is an ideal candidate to implement a III-V nucleation layer on a silicon substrate. The optimization of this nucleation has been pursued for decades, since it can form a virtual substrate to grow monolithically III-V devices. In this work we present a GaP nucleation approach using a standard MOVPE reactor with regular precursors. This design simplifies the epitaxial growth in comparison to other routines reported, making the manufacturing process converge to an industrial scale. In short, our approach intends to mimic what is done to grow multijunction solar cells on Ge by MOVPE, namely, to develop a growth process that uses a single reactor to manufacture the complete III-V structure, at common MOVPE process temperatures, using conventional precursors. Here, we present the different steps in such GaP nucleation routine, which include the substrate preparation, the nucleation itself and the creation of a p-n junction for a Si bottom cell. The morphological and structural measurements have been made with AFM, SEM, TEM and Raman spectroscopy. These results show a promising surface for subsequent III-V growth with limited roughness and high crystallographic quality. For its part, the electrical characterization reveals that the routine has also formed a p-n junction that can serve as bottom subcell for the multijunction solar cell.

DEVELOPMENT OF HIGHLY CONDUCTIVE BORON-DOPED MICROCRYSTALLINE SILICON FILMS FOR APPLICATION IN SOLAR CELLS

2006 ◽  
Vol 20 (03) ◽  
pp. 303-314 ◽  
Author(s):  
QING-SONG LEI ◽  
ZHI-MENG WU ◽  
JIAN-PING XI ◽  
XIN-HUA GENG ◽  
YING ZHAO ◽  
...  
Keyword(s):  
Solar Cells ◽  
Substrate Temperature ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Silicon Films ◽  
Microcrystalline Silicon ◽  
Very High Frequency ◽  
Boron Doped ◽  
Deposition Processes ◽  
P Type

We have examined the deposition of highly conductive boron-doped microcrystalline silicon (μc- Si:H ) films for application in solar cells. Depositions were conducted in a very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) chamber. In the deposition processes, various substrate temperatures (TS) were applied. Highly conductive p-type microcrystalline silicon films were obtained at substrate temperature lower than 210°C. The factors that affect the conductivity of the films were investigated. Results suggest that the dark conductivity, which was determined by the Hall mobility and carrier concentration, is influenced by the structure. The properties of the films are strongly dependent on the substrate temperature. With TS increasing, the dark conductivity (σd) increases initially; reach the maximum values at certain TS and then decrease. Also, we applied the boron-doped μc- Si:H as p-layers to the solar cells. An efficiency of about 8.5% for a solar cell with μc- Si:H p-layer was obtained.

SiGe Thin-Film Structures for Solar Cells

1997 ◽  
Vol 485 ◽  
Author(s):  
G. Bremond ◽  
A. Daami ◽  
A. Laugier ◽  
W. Seifert ◽  
M. Kittler ◽  
...  
Keyword(s):  
Solar Cells ◽  
Buffer Layer ◽  
Base Material ◽  
Chemical Vapor ◽  
Base Layer ◽  
Electrical Measurements ◽  
Remote Plasma ◽  
Si Substrates ◽  
Plasma Hydrogenation ◽  
Active Base

AbstractIn order to study their applicability as the active base material in Si thin crystalline film solar cell technology, SiGe relaxed layers grown by Liquid Phase Epitaxy (LPE) and Chemical Vapor Deposition (CVD) on Si substrates are investigated by optical and electrical measurements (TEM, EXD, PL, EBIC). The main results of this work is to point out the improvement of the SiGe active base layer by using smooth Ge graded SiGe buffer layer and remote plasma hydrogenation. TEM, EXD, PL experiments show the effect of the Ge graded buffer layer grown using LPE, by confining the threading dislocations in the SiGe buffer layer close to the Si/SiGe interface. EBIC measurements reveal low recombination activity of dislocations at 300 K providing the diffusion length exceeds the 15 μm layer thickness The enhanced luminescence of SiGe near bandgap indicates that remote plasma hydrogenation induces a decrease of the non-radiative recombination pathways due to dislocations on CVD layers where defect recombinations dominate as indicated by EBIC measurements.This study points out the importance of controlling relaxed SiGe layers with good minority carrier recombination quality as a key issue for the optimization of new SiGe/Si based solar cells.

Advanced deposition phase diagrams for guiding Si:H-based multijunction solar cells

2008 ◽  
Vol 354 (19-25) ◽  
pp. 2435-2439 ◽  
Author(s):  
J.A. Stoke ◽  
N.J. Podraza ◽  
Jian Li ◽  
Xinmin Cao ◽  
Xunming Deng ◽  
...  
Keyword(s):  
Solar Cells ◽  
Phase Diagrams ◽  
Multijunction Solar Cells

High Efficiency Large Area a-Si:H and a-SiGe:H Multi-junction Solar Cells Using MVHF at High Deposition Rate

2009 ◽  
Vol 1153 ◽  
Author(s):  
Xixiang Xu ◽  
Dave Beglau ◽  
Scott Ehlert ◽  
Yang Li ◽  
Tining Su ◽  
...  
Keyword(s):  
Solar Cells ◽  
High Efficiency ◽  
High Deposition Rate ◽  
Discharge Process ◽  
Large Area ◽  
Very High Frequency ◽  
Cell Structures ◽  
Evolution Characteristics ◽  
Stable Performance ◽  
Sun Light

AbstractWe have developed high efficiency large area a-Si:H and a-SiGe:H multi-junction solar cells using a Modified Very High Frequency (MVHF) glow discharge process. We conducted a comparative study for different cell structures, and compared the initial and stable performance and light-induced degradation of solar cells made using MVHF and RF techniques. Besides high efficiency, the MVHF cells also demonstrate superior light stability, showing <10% degradation after 1000 hour of one-sun light soaking at 50 °C. We also studied light-induced defect level and hydrogen evolution characteristics of MVHF deposited a-SiGe:H films and compared them with the RF deposited films.

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