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Identifying electronic properties relevant to improving stability in a-Si:H-based cells and overall performance in a-Si,Ge:H-based cells. Annual subcontract report, April 18, 1994--April 17, 1995

Description: This report describes work performed by the University of Oregon focusing on the characterization and evaluation of amorphous semiconductor materials produced by novel deposition conditions and/or methods. The results are based on a variety of junction capacitance techniques: admittance spectroscopy, transient photocapacitance (and photocurrent), and drive-level capacitance profiling. These methods allow the determination of deep defect densities and their energy distributions, Urbach bandtail … more
Date: November 1, 1995
Creator: Cohen, J.D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Identifying electronic properties relevant to improving stability in a-Si:H-based cells and overall performance in a-Si,Ge:H-based cells. Annual subcontract report, 18 April 1995--17 April 1996

Description: The work done during this second phase of the University of Oregon`s NREL subcontract focused on degradation studies in both pure a-Si:H and a-Si,Ge:H alloys, as well as a detailed study of the interface between these two materials in a-Si:H/a-Si, Ge:H heterostructures. All samples discussed in this report were produced by the glow-discharge method and were obtained either in collaboration with United Solar Systems Corporation or with researchers at Lawrence Berkeley laboratory. First, the resu… more
Date: March 1, 1997
Creator: Cohen, J.D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Identifying Electronic Properties Relevant to Improving Stability in a-Si:H-Based Cells and Overall Performance in a-Si,Ge:H-Based Cells; final Subcontract Report, 18 April 1994-15 January 1998

Description: The work carried out by the University of Oregon Under this subcontract focused on the characterization and evaluation of low-gap (a-Si,Ge:H) alloy materials and on issues related to overall stability in the mid-gap (a-SiH) materials. First, researchers characterized an extensive series of Uni-Solar a-Si,Ge:H samples using drive-level capacitance profiling and the analysis of sub-band-gap photocapacitance and photocurrent spectra. Thus, several bands of deep defect transitions were identified. … more
Date: November 16, 1998
Creator: Cohen, J. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Identifying electronic properties relevant to improving the performance and stability of amorphous silicon-based mid-gap and low-gap cells: Annual subcontract report, 16 January 1998--15 January 1999

Description: An overriding theme of the work described in this report has been the effect of partial crystallinity, or the approach to partial crystallinity, on the electronic properties of a-Si:H. This includes, of course, how degradation or the relative stability of these films is affected by the approach to, or onset of, microcrystallinity. The authors first discussed the results on a set of samples produced by dc reactive magnetron sputtering, obtained in collaboration with John Abelson's group at the U… more
Date: March 31, 2000
Creator: Cohen, J. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Identifying Electronic Properties Relevant to Improving the Performance and Stability of Amorphous Silicon Based Photovoltaic Cells: Final Subcontract Report, 27 November 2002--31 March 2005

Description: A major effort during this subcontract period has been to evaluate the microcrystalline Si material under development at United Solar Ovonics Corporation (USOC). This material is actually a hydrogenated nanocrystalline form of Si and it will be denoted in this report as nc-Si:H. Second, we continued our studies of the BP Solar high-growth samples. Third, we evaluated amorphous silicon-germanium alloys produced by the hot-wire chemical vapor deposition growth process. This method holds some pote… more
Date: November 1, 2005
Creator: Cohen, J. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Similarity-Guided Streamline Placement with Error Evaluation

Description: Most streamline generation algorithms either provide a particular density of streamlines across the domain or explicitly detect features, such as critical points, and follow customized rules to emphasize those features. However, the former generally includes many redundant streamlines, and the latter requires Boolean decisions on which points are features (and may thus suffer from robustness problems for real-world data). We take a new approach to adaptive streamline placement for steady vector… more
Date: August 15, 2007
Creator: Chen, Y.; Cohen, J. D. & Krolik, J. H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Tile-based Level of Detail for the Parallel Age

Description: Today's PCs incorporate multiple CPUs and GPUs and are easily arranged in clusters for high-performance, interactive graphics. We present an approach based on hierarchical, screen-space tiles to parallelizing rendering with level of detail. Adapt tiles, render tiles, and machine tiles are associated with CPUs, GPUs, and PCs, respectively, to efficiently parallelize the workload with good resource utilization. Adaptive tile sizes provide load balancing while our level of detail system allows tot… more
Date: August 15, 2007
Creator: Niski, K. & Cohen, J. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Identifying the Electronic Properties Relevant to Improving the Performance of High Band-Gap Copper Based I-III-VI2 Chalcopyrite Thin Film Photovoltaic Devices: Final Subcontract Report, 27 April 2004-15 September 2007

Description: This report summarizes the development and evaluation of higher-bandgap absorbers in the CIS alloy system. The major effort focused on exploring suitable absorbers with significant sulfur alloying in collaboration with Shafarman's group at the Institute of Energy Conversion. Three series of samples were examined; first, a series of quaternary CuIn(SeS)2-based devices without Ga; second, a series of devices with pentenary Cu(InGa)(SeS)2 absorbers in which the Se-to-S and In-to-Ga ratios were cho… more
Date: August 1, 2008
Creator: Cohen, J. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Investigations of the origins of metastable light-induced changes in hydrogenated amorphous silicon

Description: The work performed for this contract continued investigations of the origins of metastable effectS in a-Si:H through three kinds of studies: (1) the effect of carbon impurities in a-Si:H samples at low concentrations using drive-level capacitance profiling measurements on samples whose carbon content was intentionally modulated spatially during growth, (2) the characterization of metastable states in n-type doped a Si:H samples caused by quench cooling and by light-soaking with partial annealin… more
Date: December 1, 1991
Creator: Cohen, J.D. (Oregon Univ., Eugene, OR (United States))
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Investigations of the origins of metastable light-induced changes in hydrogenated amorphous silicon. Final subcontract report, April 1, 1988--March 31, 1991

Description: The work performed for this contract continued investigations of the origins of metastable effectS in a-Si:H through three kinds of studies: (1) the effect of carbon impurities in a-Si:H samples at low concentrations using drive-level capacitance profiling measurements on samples whose carbon content was intentionally modulated spatially during growth, (2) the characterization of metastable states in n-type doped a Si:H samples caused by quench cooling and by light-soaking with partial annealin… more
Date: December 1, 1991
Creator: Cohen, J. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Microscopic origins of metastable effects in a-Si:H and deep defect characterization in a-Si,Ge:H alloys. Annual subcontract report, 1 February 1991--31 January 1992

Description: This report describes works to use transient photocapacitance and photocurrent measurements to determine the deep defect distribution and processes in low-band-gap a-Si,Ge:H alloys. Samples for these studies were produced by the photochemical vapor deposition (photo-CVD) growth method and were obtained through a collaboration with researchers at the University of Delaware. This report discusses how a detailed comparison between the photocapacitance and photocurrent spectra can be used to separa… more
Date: July 1, 1992
Creator: Cohen, J. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Microscopic origins of metastable effects in a-Si:H and deep defect characterization in a-Si,Ge:H alloys. Final subcontract report, February 1, 1991--January 31, 1994

Description: This research supported by NREL Subcontract XG-1-10063-1 over the past three years has involved, first of all, a fairly complete characterization of a two series of a-Si{sub 1-x}Ge{sub x}:H samples: a series of 9 films grown at the University of Delaware by the photo-CVD method (for 0.29 {<=} {times} {<=} 0.62) and series of 6 films grown at U.S.S.C. by the glow discharge method (for 0.20 {<=} {times} {<=} 0.50). Both these series of samples seem to represent what is close to the {open_quotes}s… more
Date: September 1, 1994
Creator: Cohen, J. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Identifying Electronic Properties Relevant to Improving the Performance and Stability of Amorphous Silicon Based Mid-Gap and Low-Gap Cells: Final Subcontract Report, 16 January 1998-15 October 2001

Description: This report describes our experimental studies which have been concentrated in roughly five areas. Specifically: (1) We have examined a?Si:H grown very close to the microcrystalline phase boundary, so-called''edge material,'' to help understand why such material is more stable with respect to light-induced degradation; (2) We have also studied the electronic properties, and degradation characteristics of mixed phase material that is mostly a?Si:H, but which contains a significant microcrystalli… more
Date: July 1, 2002
Creator: Cohen, J. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Microscopic origins of metastable effects in a-Si:H and deep defect characterization in a-Si,Ge:H alloys. Annual subcontract report, 1 February 1992--31 January 1993

Description: This report describes work to evaluate low-mobility-gap a-Si,Ge:H alloy films. Results are based on junction capacitance techniques of admittance spectroscopy, transient photocapacitance (and photocurrent), and drive-level capacitance profiling. Eight a-Si,Ge:H alloy samples grown by photo-CVD encompassed the range of optical gaps from 1.3 to 1.6 eV, and corresponding Ge fractions from about 20 to 60 at%. We employed junction capacitance techniques to determine deep defect energies and densitie… more
Date: August 1, 1993
Creator: Cohen, J. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

a-SiGe:H Materials and Devices Deposited by Hot Wire CVD Using a Tantalum Filament Operated at Low Temperature

Description: We report the deposition of improved hydrogenated amorphous silicon germanium (a-SiGe:H) films by the hot wire CVD (HWCVD) technique using a tantalum filament operating at a low temperature. We gauge the material quality of the a-SiGe:H films by comparing infrared, small angle X-ray scattering (SAXS), photocapacitance, and conductivity measurements to earlier results, and fabricate single-junction n-i-p solar cell devices using these i-layers.
Date: February 1, 2005
Creator: Mahan, A. H.; Xu, Y.; Gedvilas, L. M.; Reedy, R. C.; Williamson, D. L.; Datta, S. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Correlation of Structural and Electronic Properties with Solar Cell Efficiency for Amorphous Silicon Deposited at Increasing Growth Rates

Description: This paper details the effects of increasing the growth rate of hydrogenated amorphous silicon (a-Si:H), deposited by dc plasma chemical vapor deposition, on the structural and electronic properties of the material in comparison with the performance of solar cells incorporating such layers. The hydrogen content exhibits the strongest correlation with the solar cell efficiency. The defect density measured by two different techniques, correlate poorly but when measured by a third technique, corre… more
Date: June 1, 2003
Creator: Ganguly, G.; Han, D.; Williamson, D. L.; Nelson, B. P. & Cohen, J. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Microscopic origins of metastable effects in a-Si:H and deep defect characterization in a-Si,Ge:H alloys

Description: This report describes works to use transient photocapacitance and photocurrent measurements to determine the deep defect distribution and processes in low-band-gap a-Si,Ge:H alloys. Samples for these studies were produced by the photochemical vapor deposition (photo-CVD) growth method and were obtained through a collaboration with researchers at the University of Delaware. This report discusses how a detailed comparison between the photocapacitance and photocurrent spectra can be used to separa… more
Date: July 1, 1992
Creator: Cohen, J. D. (Oregon Univ., Eugene, OR (United States))
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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