On the Way Towards High Efficiency Thin Film Silicon Solar Cells by the “Micromorph” Concept

1996 ◽  
Vol 420 ◽  
Author(s):  
J. Meier ◽  
P. Torres ◽  
R. Platz ◽  
S. Dubail ◽  
U. Kroll ◽  
...  
Keyword(s):  
Solar Cells ◽  
High Efficiency ◽  
Cell Structure ◽  
Microcrystalline Silicon ◽  
Very High Frequency ◽  
First Case ◽  
Efficiency Performance ◽  
Compensation Technique ◽  
Similar Cost ◽  
Very High

AbstractRecently the authors have demonstrated that compensated or “midgap” intrinsic hydrogenated microcrystalline silicon (μc-Si:H), as deposited by the Very High Frequency Glow Discharge (VHF-GD) technique, can be used as active layer in p-i-n solar cells. Compared to amorphous silicon (a-Si:H), μc-Si:H was found to have a significantly lower energy bandgap of around 1 eV. The combination of both materials (two absorbers with different gap energies) leads to a “real” tandem cell structure, which was called the “micromorph” cell. Micromorph cells can make better use of the sun's spectrum in contrast to conventional double-stacked a-Si:H / a-Si:H tandems.The present study will show that the compensation technique (involving boron “microdoping”) used sofar for obtaining midgap μc-Si:H can be replaced by the application of a gas purifier. The use of this gas purifier has a beneficial influence on the transport properties of undoped intrinsic μc-Si:H. By this procedure, increased cell efficiencies in both, single microcrystalline silicon p-i-n as well as micromorph cells could be obtained. In the first case 7.7 % stable, and in the second case 13.1% initial efficiency could be achieved under AM1.5 conditions. Preliminary light-soaking experiments performed on the tandem cells indicate that microcrystalline silicon could contribute to an enhancement of the stable efficiency performance. Micromorph cell manufacturing is fully compatible to a-Si:H technology; however, its deposition rate is still too low. With further increase of the rate, a similar cost reduction potential like in a-Si:H technology can be extrapolated.

Preparation of a-Si:H and a-SiGe:H I-Layers for Nip Solar Cells at High Deposition Rates Using a Very High Frequency Technique

1998 ◽  
Vol 507 ◽  
Author(s):  
S.J. Jones ◽  
X. Deng ◽  
T. Liu ◽  
M. Izu
Keyword(s):  
Solar Cells ◽  
Deposition Rate ◽  
High Frequency ◽  
High Efficiency ◽  
High Deposition Rate ◽  
Very High Frequency ◽  
Deposition Rates ◽  
Single Junction ◽  
Layer Deposition ◽  
Very High

ABSTRACTThe 70 MHz Plasma Enhance Chemical Vapor Deposition (PECVD) technique has been tested as a high deposition rate (10 A/s) process for the fabrication of a-Si:H and a-SiGe:H alloy ilayers for high efficiency nip solar cells. As a prelude to multi-junction cell fabrication, the deposition conditions used to make single-junction a-Si:H and a-SiGe:H cells using this Very High Frequency (VHF) method have been varied to optimize the material quality and the cell efficiencies. It was found that the efficiencies and the light stability for a-Si:H single-junction cells can be made to remain relatively constant as the i-layer deposition rate is varied from 1 to 10 Å/s. Also these stable efficiencies are similar to those for cells made at low deposition rates (1 Å/s) using the standard 13.56 MHz PECVD technique. For the a-SiGe:H cells of the same i-layer thickness, use of the VHF technique leads to cells with higher currents and an ability to more easily current match triple-junction cells prepared at high deposition rates which should lead to higher multi-junction efficiencies. Thus, use of this VHF method in the production of large area a- Si:H based multi-junction solar modules will allow for higher i-layer deposition rates, higher manufacturing throughput and reduced module cost.

High Efficiency Solar Cells with Intrinsic Microcrystalline Silicon Absorbers Deposited at High Rates by VHF-PECVD

2005 ◽  
Vol 862 ◽  
Author(s):  
Yaohua Mai ◽  
Stefan Klein ◽  
Reinhard Carius ◽  
Xinhua Geng ◽  
Friedhelm Finger
Keyword(s):  
Solar Cells ◽  
High Efficiency ◽  
Chemical Vapor ◽  
Microcrystalline Silicon ◽  
Very High Frequency ◽  
Deposition Rates ◽  
Glass Substrates ◽  
High Efficiency Solar Cells ◽  
High Frequency Plasma ◽  
Frequency Plasma

AbstractIntrinsic microcrystalline silicon (μc-Si:H ) was prepared at high deposition rates (RD) by very high frequency plasma-enhanced chemical vapor deposition (PECVD) working at high-pressure high-power (hphP). The material has similar electrical and optical properties as μc-Si:H material deposited at low rates by low-pressure low-power PECVD, apart from a more pronounced structure in-homogeneity along the growth axis for material deposited on glass substrates. With optimized deposition conditions high efficiency solar cells can be grown with deposition rates of up to 15 Å/s without deterioration of the performance as a function of RD. A high conversion efficiency of 9.8 % was obtained for a single junction μc-Si:H p-i-n solar cell at a deposition rate of RD = 11 Å/s.

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.

High-efficiency Large-area Nanocrystalline Silicon Solar Cells Using MVHF Technology

2010 ◽  
Vol 1245 ◽  
Author(s):  
Xixiang Xu ◽  
Tining Su ◽  
Scott Ehlert ◽  
David Bobela ◽  
Dave Beglau ◽  
...  
Keyword(s):  
Solar Cells ◽  
High Efficiency ◽  
Film Growth ◽  
Nanocrystalline Silicon ◽  
Large Area ◽  
Very High Frequency ◽  
Spatial Uniformity ◽  
Very High ◽  
Indoor And Outdoor ◽  
Made In

AbstractWe present the progress made in attaining high-efficiency large-area nc-Si:H based multi-junction solar cells using Modified Very High Frequency technology. We focused our effort on improving the spatial uniformity and homogeneity of nc-Si:H film growth and cell performance. We also conducted both indoor and outdoor light soaking studies and achieved 11.2% stabilized efficiency on large-area (≥400 cm2) encapsulated a-Si:H/nc-Si:H/nc-Si:H triple-junction cells.

Analysis of Plasma Properties and Deposition of Amorphous Silicon Alloy Solar Cells Using Very High Frequency Glow Discharge

1999 ◽  
Vol 557 ◽  
Author(s):  
B. Yan ◽  
J. Yang ◽  
S. Guha ◽  
A. Gallagher
Keyword(s):  
Solar Cells ◽  
High Frequency ◽  
Lower Energy ◽  
Ionic Current ◽  
Ion Bombardment ◽  
Half Width ◽  
Rf Plasma ◽  
Very High Frequency ◽  
Very High ◽  
Ionic Energy

AbstractPositive ionic energy distributions in modified very-high-frequency (MVHF) and radio frequency (RF) glow discharges were measured using a retarding field analyzer. The ionic energy distribution for H2 plasma with 75 MHz excitation at a pressure of 0.1 torr has a peak at 22 eV with a half-width of about 6 eV. However, with 13.56 MHz excitation, the peak appears at 37 eV with a much broader half-width of 18 eV. The introduction of SiH4 to the plasma shifts the distribution to lower energy. Increasing the pressure not only shifts the distribution to lower energy but also broadens the distribution. In addition, the ionic current intensity to the substrate is about five times higher for MVHF plasma than for RF plasma. In order to study the effect of ion bombardment, the deposition of a-Si alloy solar cells using MVHF was investigated in detail at different pressures and external biases. Lowering the pressure and negatively biasing the substrate increases ion bombardment energy and results in a deterioration of cell performance. It indicates that ion bombardment is not beneficial for making solar cells using MVHF. By optimizing the deposition conditions, a 10.8% initial efficiency of a-Si/a-SiGe/SiGe triple-junction solar cell was achieved at a deposition rate of 0.6 nm/sec.

Annealing Kinetics of Amorphous Silicon Alloy Solar Cells Made at Various Deposition Rates

2001 ◽  
Vol 664 ◽  
Author(s):  
Baojie Yana ◽  
Jeffrey Yanga ◽  
Kenneth Lord ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
High Frequency ◽  
Room Temperature ◽  
Defect Density ◽  
Very High Frequency ◽  
Solar Cell Performance ◽  
Kinetics Of ◽  
Very High

ABSTRACTA systematic study has been made of the annealing kinetics of amorphous silicon (a-Si) alloy solar cells. The cells were deposited at various rates using H2 dilution with radio frequency (RF) and modified very high frequency (MVHF) glow discharge. In order to minimize the effect of annealing during light soaking, the solar cells were degraded under 30 suns at room temperature to quickly reach their saturated states. The samples were then annealed at an elevated temperature. The J-V characteristics were recorded as a function of annealing time. The correlation of solar cell performance and defect density in the intrinsic layer was obtained by computer simulation. Finally, the annealing activation energy distribution (Ea) was deduced by fitting the experimental data to a theoretical model. The results show that the RF low rate solar cell with high H2 dilution has the lowest Ea and the narrowest distribution, while the RF cell with no H2 dilution has the highest Ea and the broadest distribution. The MVHF cell made at 8Å/s withhigh H2 dilution shows a lower Ea and a narrower distribution than the RF cell made at 3 Å/s, despite the higher rate. We conclude that different annealing kinetics plays an important role in determining the stabilized performance of a-Si alloy solar cells.

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