Recombination in n-i-p (Substrate) a-Si:H Solar Cells with Silicon Carbide and Protocrystalline p-Layers

2003 ◽  
Vol 762 ◽  
Author(s):  
V. Vlahos ◽  
J. Deng ◽  
J.M. Pearce ◽  
R.J. Koval ◽  
G.M. Ferreira ◽  
...  
Keyword(s):  
Solar Cells ◽  
Forward Bias ◽  
Open Circuit ◽  
High Hydrogen ◽  
Beneficial Effects ◽  
Hydrogen Dilution ◽  
Cell Structures ◽  
Current Characteristics ◽  
Hydrogenated Amorphous

AbstractA study was carried out on hydrogenated amorphous silicon (a-Si:H) n-i-p (substrate) solar cell structures with p-a-SiC:H and highly diluted p-Si:H layers grown with different dilution ratios R=[H2]/[SiH4]. The contributions of the recombination at the p/i interfaces to the forward bias dark current characteristics were identified and quantified for the different cell structures. In both cell structures the role of the p/i interfaces was identified and it is found that the lowest p/i interface recombination is obtained with protocrystalline p-Si:H layers having no microcrystalline component. The results with p-Si:H layers are attributed not only to their properties but also to the subsurface modification of the intrinsic layer. Evidence is also presented that points to the beneficial effects of the high hydrogen dilution and power used in the deposition of these p-layers in creating the p/i interface regions. The limitations on 1 sun open circuit voltage (VOC) imposed by the p/i recombination present in all the cell structures is consistent with the mechanisms proposed by Deng et al.[1]. The results presented here also point to why the 1 sun VOC in protocrystalline p-Si:H solar cells is higher than that in p-a-SiC:H cells.

Development of Stable a-Si/a-SiGe Tandem Solar Cell Submodules Deposited by a Very High Hydrogen Dilution at Low Temperature

1998 ◽  
Vol 507 ◽  
Author(s):  
Masaki Shima ◽  
Masao Isomura ◽  
Eiji Maruyama ◽  
Shingo Okamoto ◽  
Hisao Haku ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Silicon Germanium ◽  
Structural Variations ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Hydrogen Radicals ◽  
Amorphous Silicon Germanium ◽  
Hydrogenated Amorphous ◽  
Very High

ABSTRACTThe world's highest stabilized efficiency of 9.5% (light-soaked and measured by the Japan Quality Assurance Organization (JQA)) for an a-Si/a-SiGe superstrate-type solar cell submodule (area: 1200 cm2) has been achieved. This value was obtained by investigating the effects of very-high hydrogen dilution of up to 54:1 (= H2: SiH4) on hydrogenated amorphous silicon germanium (a-SiGe:H) deposition at a low substrate temperature (Ts). It was found that deterioration of the film properties of a-SiGe:H when Ts decreases under low hydrogen dilution conditions can be suppressed by the high hydrogen dilution. This finding probably indicates that the energy provided by hydrogen radicals substitutes for the lost energy caused by the decrease in Ts and that sufficient surface reactions can occur. In addition, results from an estimation of the hydrogen and germanium contents of a-SiGe:H suggest the occurrence of some kinds of structural variations by the high hydrogen dilution. A guideline for optimization of a-SiGe:H films for solar cells can be presented on the basis of the experimental results. The possibility of a-SiGe:H as a narrow gap material for a-Si stacked solar cells in contrast with microcrystalline silicon (μ c-Si:H) will also be discussed from various standpoints. At present, a-SiGe:H is considered to have an advantage over μ1 c-Si:H.

Film and Solar Cell Properties of a-SiC:H Alloys

1992 ◽  
Vol 258 ◽  
Author(s):  
Yuan-Min Li ◽  
A. Catalano ◽  
B.F. Fieselmann
Keyword(s):  
Open Circuit ◽  
The Novel ◽  
High Hydrogen ◽  
Cell Efficiency ◽  
Hydrogen Dilution ◽  
Silicon Carbon ◽  
Degradation Rates ◽  
Cell Stability ◽  
Hydrogenated Amorphous ◽  
Substrate Temperatures

ABSTRACTHydrogenated amorphous silicon-carbon alloys (a-SiC:H) with 1.9–2.0 eV bandgaps have been grown by glow-discharge using methane as the source of carbon with high hydrogen dilution (CH4+H2) at various substrate temperatures. A thickness dependence of the properties of un-doped films is observed. The photo-electronic properties have been much improved in these undoped alloys compared to those of CH4 based films without H-dilution, however the CH4+H2 based boron doped a-SiC:H films show little improvement. Simple p-i-n single junction solar cells using improved wide-gap a-SiC:H Mayers, based on the CH4+H2 recipe and the novel carbon feedstock trisilylmethane (TSM), show high open circuit voltages and high fill factors. The cell stability under illumination has been tested. There is no correlation in degradation rates between the a-SiC:H cell efficiency and the photoconductivity of the corresponding i-layer films.

Amorphous Silicon-Carbon Alloys for Solar Cells

1993 ◽  
Vol 297 ◽  
Author(s):  
Yuan-Min Li
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
Light Exposure ◽  
Open Circuit ◽  
Hydrogen Dilution ◽  
Silicon Carbon ◽  
Hydrogenated Amorphous ◽  
Substrate Temperatures ◽  
Open Circuit Voltages

Recent efforts to optimize undoped, glow-discharge hydrogenated amorphous silicon-carbon alloys (a-SiC:H) with 1.9-2.0 eV bandgaps for solar cell applications are reviewed. Hydrogen dilution coupled with relatively low substrate temperatures (below 200 °C) have led to great improvements in the optical and phototransport properties of a-SiC:H films. The issue of alternative carbon feedstocks other than methane (CH4) will be explored. The improved a-SiC:H alloys have resulted in solar cells with high open circuit voltages (V∞ > 1.0 volt) and high fill factors (> 0.7). Further, the a-SiC:H solar cell instability upon prolonged light exposure has been much reduced. Correlation will be made between the properties of bulk undoped a-SiC:H films and the performance of p-i-nsingle junction solar cells using corresponding a-SiC:H thin i-layers.

Properties of a-SiC:H films and solar cells

2000 ◽  
Vol 77 (9) ◽  
pp. 699-704
Author(s):  
R Gharbi ◽  
M Fathallah ◽  
C F Pirri ◽  
E Tresso ◽  
G Crovini ◽  
...  
Keyword(s):  
Solar Cells ◽  
Vapor Deposition ◽  
Open Circuit Voltage ◽  
Energy Gap ◽  
Chemical Vapor ◽  
Open Circuit ◽  
Light Illumination ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Effect Of Light

a-SiC:H samples and solar cells were made by plasma-enhanced chemical vapor deposition (PECVD) using a multichamber deposition system. The effect of light illumination on samples prepared with and without hydrogen dilution was studied. The phototransport properties of the samples prepared with high hydrogen dilution were more stable versus time of illumination than non diluted ones.The samples were inserted as an intrinsic layer in semitransparent solar cells. The performance of solar cells depends on the energy gap and thickness of the intrinsic layer. High hydrogen dilution may increase the energy gap and act to decrease the structure uniformity. The results show that open circuit voltage Voc decreases with light illumination and depends on the doped p+ layer quality and created defects in the intrinsic layer. PACS Nos.: 70, 72, 40

Characterization of the Bulk Recombination in Hydrogenated Amorphous Silicon Solar Cells

2004 ◽  
Vol 808 ◽  
Author(s):  
J. Deng ◽  
J.M. Pearce ◽  
V. Vlahos ◽  
R.W. Collins ◽  
C.R. Wronski
Keyword(s):  
Solar Cells ◽  
Amorphous Silicon ◽  
Forward Bias ◽  
Hydrogenated Amorphous Silicon ◽  
Quality Factors ◽  
Defect States ◽  
Cell Structures ◽  
Staebler Wronski Effect ◽  
Hydrogenated Amorphous

ABSTRACTDark forward bias current, JD-V, characteristics offer a probe for characterizing carrier recombination and the defect states in the intrinsic layers of hydrogenated amorphous silicon (a-Si:H) solar cells. Detailed studies were carried out on such characteristics for the cells with optimized p/i interfaces and high quality i-layers in which the current transport is bulk recombination dominated. It was found that the diode quality factor n is not a constant with bias voltages as has been generally considered. Instead, it can be best described through the bias dependent differential diode quality factors, n(V) = [kT/q]−1[d(lnJD)/dV]−1, whose magnitude and shape reflect the gap state distribution in the corresponding bulk i-layers. The n(V) characteristics obtained on cell structures with both hydrogen diluted and undiluted i-layers have been utilized in characterizing the differences in the distribution of defect states in the two i-layers both in annealed state as well as after creating light induced defects. In the characterization of the Staebler-Wronski Effect (SWE) using JD-V characteristics, a newphenomenon is observed – relaxation of light induced defect states created by 1 sun illumination at 25°C, which is also found in the follow-on studies on the photo-conductivities of corresponding thin films.

Carrier Transport and Recombination In A-SI:H P-I-N Solar Cells in Dark and Under Illumination

2003 ◽  
Vol 762 ◽  
Author(s):  
J. Deng ◽  
J.M. Pearce ◽  
V. Vlahos ◽  
R.J. Koval ◽  
R.W. Collins ◽  
...  
Keyword(s):  
Solar Cells ◽  
Carrier Transport ◽  
Short Circuit ◽  
Forward Bias ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Potential Barriers ◽  
Carrier Lifetimes ◽  
Wide Range

AbstractA study has been carried out on the forward bias dark current and the short circuit current -open circuit voltage characteristics of a-Si:H p-i-n solar cells over wide range of illumination intensities. Results are presented with superposition of these characteristics over extended current voltage regimes. This and the observed separation between these characteristics are consistent with the arguments presented based on first principle arguments. The conclusions drawn about the role of photo-generated carrier lifetimes, the densities of defects and the potential barriers in the i-layers adjacent to the n and p contacts are confirmed by numerical simulations. The key role of these potential barriers to the split in the characteristics offer new insight into both why the lack of superposition has been observed and the erroneous conclusions drawn about carrier transport for a-Si:H solar cells in the dark and under illumination.

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