scholarly journals Hydrogenated Microcrystalline Silicon: From Material to Solar Cells

2000 ◽  
Vol 609 ◽  
Author(s):  
N. Wyrsch ◽  
C. Droz ◽  
L. Feitknecht ◽  
M. Goerlitzer ◽  
U. Kroll ◽  
...  
Keyword(s):  
Solar Cells ◽  
Transport Properties ◽  
Defect Density ◽  
Chemical Vapour ◽  
Impurity Content ◽  
Quality Parameter ◽  
Oxygen Impurity ◽  
Microcrystalline Silicon ◽  
Cell Efficiency ◽  
Hydrogen Dilution

ABSTRACTUndoped hydrogenated microcrystalline silicon (νc-Si:H) layers and solar cells have been deposited by plasma-enhanced chemical vapour at low temperature and at different values of VHF plasma power and silane to hydrogen dilution ratios. Transport and defect density measurements on layers suggest that structural properties (e.g. crystallite shape and size) only marginally influence the electronic transport properties. The latter are influenced strongly by the Fermi level, which depends on the oxygen impurity content. Furthermore, they are best described by the quality parameter ν0τ0 (deduced from photoconductivity and ambipolar diffusion length). Cell efficiency correlates better with νoτ0 than with the defect density as determined from subbandgap absorption. Anisotropy of the transport properties in some νc-Si:H is also demonstrated but does not seem to play a major role in νc-Si:H cells deposited at high rates under VHF glow discharge conditions.

Investigation of the Electronic Transport in Pin Solar Cells Based on Microcrystalline Silicon by 2D Numerical Modeling

1998 ◽  
Vol 507 ◽  
Author(s):  
J. Zimmer ◽  
H. Stiebig ◽  
H. Wagner
Keyword(s):  
Numerical Modeling ◽  
Solar Cells ◽  
Grain Boundaries ◽  
Transport Properties ◽  
Amorphous Phase ◽  
Electronic Transport ◽  
Crystalline Silicon ◽  
Defect Density ◽  
Simulated Data ◽  
Microcrystalline Silicon

ABSTRACTWe investigated the transport and recombination behavior of pin solar cells based on micro- crystalline silicon (μc-Si:H). A comparison of experimental and simulated data of the dark I/V- curves, the I/V-behavior under AM1.5 illumination as well as the quantum efficiency reveals an enhanced defect density in μc-Si:H compared to c-Si which could be located as defect rich grain boundaries around the crystallites. Further, in case there is amorphous phase in the material, the distribution of a-Si:H around the crystallites is unlikely, since the electronic transport properties are disturbed, whereas an arrangement in the shape of extended areas does not affect the transport behavior significantly due to occurrence of percolation.

Improved Efficiency of Single Junction Microcrystalline Silicon n-i-p Solar Cells with an i-Layer Made by Hot-Wire CVD

2007 ◽  
Vol 989 ◽  
Author(s):  
Hongbo Li ◽  
Ronald H.J. Franken ◽  
Robert L. Stolk ◽  
C. H.M. van der Werf ◽  
Jan-Willem A. Schuttauf ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Solar Cells ◽  
Chemical Vapour Deposition ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Hot Wire ◽  
Microcrystalline Silicon ◽  
Single Junction ◽  
Layer Deposition ◽  
P Cells

AbstractThe influence of the surface roughness of Ag/ZnO coated substrates on the AM1.5 J-V characteristics of microcrystalline silicon (μc-Si:H) solar cells with an i-layer made by the hot-wire chemical vapour deposition (HWCVD) technique is discussed. Cells deposited on substrates with an intermediate rms roughness show the highest efficiency. When using reverse hydrogen profiling during i-layer deposition, an efficiency of 8.5 % was reached for single junction μc-Si:H n-i-p cells, which is the highest for μc-Si:H n-i-p cells with a hot-wire i-layer.

Mechanism of the Improvement in Microcrystalline Silicon Solar Cells by Hydrogen Plasma Treatment

2013 ◽  
Vol 773 ◽  
pp. 118-123
Author(s):  
Jing Yan Li ◽  
Xiang Bo Zeng ◽  
Hao Li ◽  
Xiao Bing Xie ◽  
Ping Yang ◽  
...  
Keyword(s):  
Solar Cells ◽  
Electric Field ◽  
Plasma Treatment ◽  
Defect Density ◽  
Hydrogen Plasma ◽  
Microcrystalline Silicon ◽  
One Dimensional ◽  
Long Wavelength ◽  
Drift Length ◽  
Experimental Improvement

We explain the experimental improvement in long wavelength response by hydrogen plasma treatment (HPT) in n/i interface. The absorption coefficient of the intrinsic microcrystalline silicon (μc-Si) is decreased in the low energy region (0.8~1.0 eV) by HPT, which indicates a lower defect density in μc-Si layer deposited with HPT than its counterpart without HPT. Simulation by one-dimensional device simulation program for the Analysis of Microelectronic and Photonic Structures (AMPS-1D) shows a higher long wavelength response in μc-Si solar cell if the defect density in intrinsic μc-Si layer is smaller. Our simulation results also disclose that the less defect density in intrinsic layer, the lower recombination rate and the higher electric field is. Higher electric field results in longer drift length which will promote collection of carriers generated by photons with long wavelength. Thus we deduce that HPT decreased defect density in absorber layer and improved the performance of μc-Si solar cells in long wavelength response.

Development of a-SiOx:H/a-Si1-xGex:H Tandem Solar Cell for Triple-Junction Solar Cell Applications

2012 ◽  
Vol 1426 ◽  
pp. 125-130
Author(s):  
Y.W. Tseng ◽  
Y.H. Lin ◽  
H.J. Hsu ◽  
C.H. Hsu ◽  
C.C. Tsai
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Silicon Oxide ◽  
Defect Density ◽  
Tandem Solar Cell ◽  
Tandem Solar Cells ◽  
Single Junction ◽  
Cell Efficiency ◽  
Photo Response ◽  
Hydrogenated Amorphous

ABSTRACTIn this work, the development of hydrogenated amorphous silicon oxide (a-SiOx:H) absorber, a-SiOx:H single-junction solar cells and a-SiOx:H/a-Si1-xGex:H tandem solar cells were presented. The oxygen content of the a-SiOx:H materials controlled by changing CO2-to-SiH4 flow ratio had significant influence on its opto-electrical property. As CO2/SiH4 increased from 0 to 2, the bandgap increased from 1.75 to 2.13 eV while the photo-conductivity decreased from 8.25×10-6 to 1.02×10-8 S/cm. Photo-response of over 105 can be obtained as the bandgap was approximately 1.90 eV. The performance of single-junction solar cells revealed a better efficiency can be obtained as the absorber bandgap was in the range of 1.83 to 1.90 eV. Further increase of the absorber bandgap may lead to the increase in bulk defect density which deteriorated the cell efficiency. Finally, a-SiOx:H/a-Si1-xGex:H tandem solar cell was fabricated with the absorber bandgap of 1.90 eV in the top cell. By matching the current between the component cells, the tandem cell efficiency of 7.38% has been achieved.

Improved Ambipolar Diffusion Length in a-Si1-xGex:H Alloys for Multi-Junction Solar Cells

1995 ◽  
Vol 377 ◽  
Author(s):  
J. Fölsch ◽  
F. Finger ◽  
T. Kulessa ◽  
F. Siebke ◽  
W. Beyer ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Silicon Germanium ◽  
Diffusion Length ◽  
Defect Density ◽  
Chemical Vapour ◽  
Film Structure ◽  
Ambipolar Diffusion ◽  
Active Layer Thickness ◽  
Solar Cell Performance

ABSTRACTTo prepare hydrogenated amorphous silicon-germanium alloys as low gap material for multi-junction solar cells in plasma enhanced chemical vapour deposition, the well established concept of strong dilution of the process gases with hydrogen has been used. Two different regimes of alloying were found: for low Ge content (x < 0.40) we observe material with low defect density, small Urbach energy and high values of the ambipolar diffusion length. In the regime of high Ge content (x > 0.40) the defect densities and Urbach energies are high and the values of the ambipolar diffusion length low. The transition is accompanied by the appearance of a low-temperature peak in hydrogen effusion experiments indicating a void rich film structure. Material from just above and below the transition zone is used in pin solar cells leading to a much enhanced red response compared with a-Si:H cells. The differences seen in the material quality are mirrored in the solar cell properties. By carefully adjusting the active layer thickness material with low diffusion length shows also reasonable solar cell performance.

Structural and optoelectronic properties of amorphous and microcrystalline silicon deposited at low substrate temperatures by RF and HW CVD

1999 ◽  
Vol 557 ◽  
Author(s):  
P. Alpuim ◽  
V. Chu ◽  
J. P. Conde
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Defect Density ◽  
Chemical Vapor ◽  
Optoelectronic Properties ◽  
Microcrystalline Silicon ◽  
Crystalline Fraction ◽  
Hydrogen Dilution ◽  
Structural And Optoelectronic Properties ◽  
Substrate Temperatures

AbstractThe structural and optoelectronic properties of silicon thin films prepared by hot wire chemical vapor deposition and radio frequency plasma enhanced chemical vapor deposition are studied in the range of substrate temperatures (Tsub)from 100 °C to 25 °C. The defect density, structure factor and bond angle disorder of amorphous silicon films (a-Si:H) deposited by both techniques are strongly improved by the use of hydrogen dilution. Correlation of these structural properties with important optoelectronic properties, such as photo-to-dark conductivity ratio, is made. Microcrystalline silicon (μc-Si:H) is obtained using HW with a large crystalline fraction for hydrogen dilutions above 85% independently of Tsub. The deposition of μc-Si:H by RF requires increasing the hydrogen dilution and shows decreasing crystalline fraction as Tsub is decreased. The properties of the low Tsub films are compared to those of samples produced at 175 °C and 250 °C in the same reactors.

Influence of Pressure and Plasma Potential on High Growth Rate Microcrystalline Silicon Grown by Vhf Pecvd

2005 ◽  
Vol 862 ◽  
Author(s):  
A. Gordijn ◽  
J. Francke ◽  
L. Hodakova ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Solar Cells ◽  
High Pressures ◽  
Defect Density ◽  
Plasma Potential ◽  
High Rate ◽  
Growth Surface ◽  
Microcrystalline Silicon ◽  
Ion Energy ◽  
Single Junction ◽  
External Power Source

AbstractMicrocrystalline silicon (μc-Si) based single junction solar cells are deposited by VHF PECVD using a showerhead cathode at high pressures in depletion conditions. At a deposition rate of 4.5 nm/s, a stabilized conversion efficiency of 6.7 % is obtained for a single junction solar cell with a μc-Si i-layer of 1 μm. The i-layer is made near the transition from amorphous to crystalline. In order to control the material properties in the growth direction, the hydrogen dilution of silane in the gas phase is graded following different profiles with a parabolic shape. It is observed that the performance of solar cells deposited at high rate improves under light soaking conditions at 50 °C, which we attribute to post deposition equilibration of a fast deposited transition material.The performance is lower at higher rates due to poorer i-layer quality (higher defect density), which may be attributed to smaller relaxation times for growth precursors at the growth surface and the higher energy ion bombardment at higher plasma power. High process pressures can be used to reduce the ion energy by decreasing the mean free path. We have introduced an additional method to limit the ion energy by controlling the DC self bias voltage using an external power source. In this way the quality of the μc-Si layers and the performance of the solar cells is further improved.

Investigation of Textured Back Reflectors for Microcrystalline Silicon Based Solar Cells

1999 ◽  
Vol 557 ◽  
Author(s):  
O. Kluth ◽  
O. Vetterl ◽  
R. Carius ◽  
F. Finger ◽  
S. Wieder ◽  
...  
Keyword(s):  
Solar Cells ◽  
Near Infrared ◽  
Spectral Response ◽  
Short Circuit ◽  
Chemical Vapour ◽  
Root Mean Square Roughness ◽  
Microcrystalline Silicon ◽  
Feature Size ◽  
Long Wavelength ◽  
Back Reflectors

AbstractMicrocrystalline silicon (μc-Si:H) solar cells require an effective light trapping in the near infrared (NIR) to enhance the long wavelength spectral response. For this purpose we investigated back reflectors based on texture-etched ZnO/Ag stacks prepared on glass substrates by magnetron sputtering. With decreasing sputter pressure the resulting surface texture of the glass/Ag/ZnO substrates after etching exhibits a larger feature size and root mean square roughness. The increase in feature size corresponds to an increase of diffuse reflectivity. Applied in microcrystalline solar cells prepared by VHF plasma enhanced chemical vapour deposition (PECVD), the reflectors showing the largest feature size (prepared at the lowest possible sputter pressure) yielded the highest long wavelength spectral response. The μc-Si n-i-p cells prepared on the latter back reflector exhibited efficiencies of 6.9 % (short circuit current density jsc= 18.8 mA/cm2) and 7.5 % (jsc=25 mA/cm2) for an i-layer thickness of 1 μm and 3.5 μm, respectively.

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