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Direct Write Processing for Photovoltaic Cells

Description: Direct writing of solar cell components is an attractive processing approach. We have fabricated a 6.8% Si solar cell using silver ink based electrodes. Ohmic contact through the antireflection (AR) coating was obtained with pure Ag electrodes at 850 0C. We also report on highly conductive silver metallizations and initial results on direct-write TCO demonstrating a 100-micron spatial resolution produced by inkjet printing.
Date: August 1, 2002
Creator: Rivkin, T.; Curtis, C.; Miedaner, A.; Perkins, J.; Alleman, J. & Ginley, D.
Partner: UNT Libraries Government Documents Department

Ink Jet Printing Approaches to Solar Cell Contacts

Description: We are developing inkjet printing as a low cost, high through-put approach to the deposition of front contacts for Si solar cells. High deposition rates of 1m per printing pass were achieved with a new metalorganic ink composed of silver (trifluoroacetate) in ethylene glycol. The printing conditions were optimized to achieve a relatively high line resolution of 120 m. The optimal parameters for the piezoelectric inkjet were a pulse frequency of 50 Hz and pulse amplitude of 25 V. The best resolution and the line quality were achieved at a substrate temperature of 180 C and drop separation of 40 m.
Date: May 1, 2003
Creator: Kaydanova, T.; Miedaner, A.; Curtis, C.; Perkins, J.; Alleman, J. & Ginley, D.
Partner: UNT Libraries Government Documents Department

Metallizations by Direct-Write Inkjet Printing: Preprint

Description: Presented at the 2001 NCPV Program Review Meeting: Direct-write technologies offer the potential for low-cost, materials-efficient deposition of contact metallizations for PV. Direct-write technologies offer the potential for low-cost materials-efficient deposition of contact metallizations for photovoltaics. We report on the inkjet printing of metal organic decomposition (MOD) inks with and without nanoparticle additions. Near-bulk conductivity of printed and sprayed metal films has been achieved for Ag and Ag nanocomposites. Good adhesion and ohmic contacts with a measured contact resistance of 400 {mu}{Omega} {center_dot} cm{sup 2} have been observed between the sprayed silver films and a heavily doped n-type layer of Si. Inkjet printed films show adhesion differences as a function of the process temperature and solvent. Silver lines with good adhesion and conductivity have been printed on glass with 100 {micro}m resolution.
Date: October 1, 2001
Creator: Curtis, C. J.; Rivkin, T.; Miedaner, A.; Alleman, J.; Perkins, J.; Smith, L. et al.
Partner: UNT Libraries Government Documents Department

Electrodeposition of CuIn1-xGaxSe2 Materials for Solar Cells:

Description: This report describes our scientific understanding of the CIGS materials system, solar cells, and processes. Through DOE support, the investigators developed much of the technology and device fabrication infrastructure applied to electrodeposited (ED) materials. The electrodeposition process is simple and fast, and can synthesize multinary precursors for subsequent processing into CuInxGa1-xSe2 (CIGS) thin-film absorbers for solar cells. The device fabricated by using electrodeposited CIGS precursor layers resulted in total-area conversion efficiencies up to 15.4%. As-deposited precursors are Cu-rich CIGS. Additional In, Ga, and Se (up to 50%) are added to the precursor films by physical vapor deposition (PVD) to adjust the final semiconductor film composition to about Cu0.95In0.75Ga0.25Se2. The ED device parameters are compared with those of an 18.8% PVD device. The tools used for comparison are current-voltage, capacitance-voltage, and spectral response characteristics. The individual parameters of the device prepared from ED precursor films showed no significant deterioration from those of the PVD CIGS cells. We also developed a buffer-based electrodeposition bath. Using the buffer solution enhances the stability of the electrodeposition process, and no metal oxides or hydroxides precipitate out of the solution. The buffer-based bath also deposits more gallium in the precursor films. As-deposited precursors are stoichiometric or slightly Cu-rich CIGS. Only a minimal amount (5%-10% of total materials) of indium was added to the ED precursor films by PVD to obtain a 9.4%-efficient device. In general, the films and devices have been characterized by inductively coupled plasma spectrometry, Auger electron spectroscopy, X-ray diffraction, electron-probe microanalysis, current-voltage, capacitance-voltage, and spectral response.
Date: October 1, 2002
Creator: Bhattacharya, R. N.; Fernandez, A. M.; Batchelor, W.; Alleman, J.; Keane, J.; Althani, H. et al.
Partner: UNT Libraries Government Documents Department

Carbon Single-Wall Nanatube Growth in a Volumetrically Confined Arc Discharge System

Description: Carbon nanotubes hold significant promise for a vast number of materials applications due to their unique mechanical, electrical, and gas storage properties. Although carbon single-wall nanotubes (SWNTs) have been synthesized since 1993 by the arc discharge method, and numerous other synthesis methods have since been developed, no method has yet produced 100% pure carbon nanotubes. Instead, a significant amount of impurities—various carbon structures and metal catalysts—are present in the raw soot. While arc discharge was the first method for SWNT synthesis, it also produces more impure raw soot in comparison to the more recently developed laser vaporization, which has produced the purest raw soot to date but is much slower. Geometry and thermal gradient are appreciably different between traditional arc discharge systems and laser vaporization systems. We report that, by incorporating some characteristics inherent to a laser vaporization system into an arc discharge system, improvement in the yield of SWNT raw soot may be achieved. This is accomplished by confining the arc within a 50 mm diameter quartz tube, similar to laser vaporization. We find through transmission electron microscopy and Raman spectroscopy that SWNTs are made in significant numbers in this confined arc discharge system, comparable to laser vaporization synthesized material. Further study is, however, required to prove reproducibility and attain an exact value for the purity of the produced raw soot.
Date: January 1, 2004
Creator: Franz, K.J.; Alleman, J.L.; Jones, K.M.; Dillon, A.C. & Heben, M.J.
Partner: UNT Libraries Government Documents Department

Transparent Conducting Contacts Based on Zinc Oxide Substitutionally Doped with Gallium: Preprint

Description: Transparent conducting oxides (TCOs) are a critical element in photovoltaic devices. This paper describes research on Ga:ZnO (a TCO candidate) using a high-throughput combinatorial approach.
Date: May 1, 2008
Creator: Gorrie, C. W.; Reese, M.; Perkins, J. D.; Alleman, J. L.; S., Dabney M.; To, B. et al.
Partner: UNT Libraries Government Documents Department

Optimization of Conductivity and Transparency in Amorphous In-Zn-O Transparent Conductors: Preprint

Description: Amorphous mixed metal oxide TCOs are of increasing interest due to the excellent opto-electronic properties and smoothness (RRMS < 0.5 nm) obtained for sputtered films deposited at less than 100 ..deg..C. Here, we have investigated the combined materials phase space of oxygen stoichiometry and metals composition (In:Zn ratio) and made two key discoveries.
Date: May 1, 2008
Creator: Perkins, J.; Berry, J.; van Hest, M.; Alleman, J.; Dabney, M.; Gedvilas, L. et al.
Partner: UNT Libraries Government Documents Department

Effect of Mo Back Contact on Na Out-Diffusion and Device Performance of Mo/Cu(In,Ga)Se2/CdS/ZnO Solar Cells: Preprint

Description: This conference paper describes the molybdenum thin films that were deposited on soda lime glass (SLG) substrates using direct-current planar magnetron sputtering, with a sputtering power density of 1.2 W/cm2. The working gas (Ar) pressure was varied from 0.6 to 16 mtorr to induce changes in the Mo films' morphology and microstructure. Thin films of Cu(In,Ga)Se2 (CIGS) were deposited on the Mo-coated glass using the 3-stage co-evaporation process. The morphology of both the Mo-coated SLG and the CIGS thin films grown on it was examined using high-resolution scanning electron microscopy. Na was depth profiled in the Mo and CIGS films by secondary ion mass spectrometry. The device performance was evaluated under standard conditions of 1000 W/m2 and 25 C. Optimum device performance is found for an intermediate Mo sputtering pressure.
Date: May 1, 2002
Creator: Al-Thani, H. A.; Hasoon, F. S.; Young, M.; Asher, S.; Alleman, J. L.; Al-Jassim, M. M. et al.
Partner: UNT Libraries Government Documents Department

Investigation of the Microstructure of Cu(In,Ga)Se2 Thin Films Used in High-Efficiency Devices: Preprint

Description: This conference paper describes the microstructure of Cu(In,Ga)Se2 (CIGS) films, as it transitioned from Cu-rich to In-rich composition, by transmission electron microscopy, and energy-dispersive X-ray spectroscopy. We find that the Cu-rich samples have larger grains than the In-rich samples, and they contain two structurally different forms of the CuxSe secondary phase. These samples also show sub-interfaces about 0.2 ..mu..m below the surface. The In-rich samples were almost void of these sub-interfaces.
Date: May 1, 2002
Creator: Noufi, R.; Yan, Y.; Abu-Shama, J.; Jones, K.; Al-Jassim, M.; Keyes, B. et al.
Partner: UNT Libraries Government Documents Department

Amorphous Transparent Conducting Oxides (TCOs) Deposited at T 100<= ..deg.. C

Description: The summary of this report is that amorphous InZnO (a-IZO) is a very versatile TCO with: (1) low process temperatures ({approx} 100 C); (2) easy to make by sputtering; (3) excellent optical and electronic properties; (4) very smooth etchable films; and (5) remarkable thermal processing stability.
Date: May 1, 2006
Creator: Perkins, J.; van Hest, M.; Teplin, C.; Alleman, J.; Dabney, M.; Gedvilas, L. et al.
Partner: UNT Libraries Government Documents Department

Recent Progress in CIGS Thin Film Solar Cell Research at NREL: Preprint

Description: Presented at the 2001 NCPV Program Review Meeting: This paper summarizes our work toward improving reproducibility in fabricating high efficiency absorbers and devices. This paper summarizes our work toward improving reproducibility in fabricating high efficiency absorbers and devices. This resulted in the fabrication of a CIGS cell with an efficiency of 21% under concentrated light. We compare devices fabricated with CdS and with Cd solution treatment alone. A high conversion efficiency of 15.7% is obtained with the latter, and we attribute this to the n-type doping afforded by Cd. The work is extended to absorbers provided by Siemens Solar Industries (SSI).
Date: October 1, 2001
Creator: Ramanathan, K.; Hasoon, F. S.; Al-Thani, H.; Alleman, J.; Keane, J.; Dolan, J. et al.
Partner: UNT Libraries Government Documents Department

Application of Combinatorial Tools for Solar Cell Improvement -- New High Performance Transparent Conducting Oxides

Description: Transparent conducting oxides (TCOs) can serve a variety of important functions in thin film photovoltaics such as transparent electrical contacts, antireflection coatings and chemical barriers. Two areas of particular interest are TCOs that can be deposited at low temperatures and TCOs with high carrier mobilities. We have employed combinatorial high-throughput approaches to investigate both these areas. Conductivities of s = 2500 W-1-cm-1 have been obtained for In-Zn-O (IZO) films deposited at 100 C and s &gt; 5000 W-1-cm-1 for In-Ti-O (ITiO) and In-Mo-O (IMO) films deposited at 550 C. The highest mobility obtained was 83 cm2/V-sec for ITiO deposited at 550 C.
Date: January 1, 2005
Creator: Perkins, J.; Taylor, M.; van Hest, M.; Teplin, C.; Alleman, J.; Dabney, M. et al.
Partner: UNT Libraries Government Documents Department

Direct-Write Contacts for Solar Cells

Description: We report on our project to develop inkjet printable contacts for solar cells. Ag, Cu, and Ni metallizations were inkjet printed with near vacuum deposition quality. Thick, highly conducting lines of Ag and Cu demonstrating good adhesion to glass, Si, and PCB have been printed at 100-200 C in air and N2, respectively. Ag grids were inkjet-printed on Si solar cells and fired through silicon nitride AR layer at 850 C resulting in 8% cells. Next-generation multicomponent inks (including etching agents) have also been developed with improved fire-through contacts leading to higher cell efficiencies. The approach developed can be easily extended to other conductors such as Pt, Pd, and Au, etc. In addition, PEDOT-PSS polymer-based conductors were inkjet-printed with the conductivity as good or better than those of polymer-based conductors.
Date: January 1, 2005
Creator: Kaydanova, T.; van Hest, M.F.A.M.; Miedaner, A.; Curtis, C. J.; Alleman, J. L.; Dabney, M. S. et al.
Partner: UNT Libraries Government Documents Department

Direct Write Contacts for Solar Cells

Description: Ag, Cu, and Ni metallizations were inkjet-printed with near-vacuum deposition quality. The approach developed can be easily extended to other conductors such as Pt, Pd, and Au. Thick, highly conducting lines of Ag and Cu demonstrating good adhesion to glass, Si, and PCB have been printed at 100-200 C in air and N2, respectively. Ag grids were inkjet-printed on Si solar cells and fired through the silicon nitride antireflective layer at 850 C resulting in 8%-efficient cells. Next-generation multicomponent inks (including etching agents) have also been developed with improved fire-through contacts leading to higher cell efficiencies. PEDOT-PSS polymer-based conductors were inkjet-printed with conductivity as good or better than that of spin-coated films.
Date: February 1, 2005
Creator: Kaydanova, T.; van Hest, M. F. A. M.; Miedaner, A.; Curtis, C. J.; Alleman, J. L.; Dabney, M. S. et al.
Partner: UNT Libraries Government Documents Department

Combinatorial Exploration of Novel Transparent Conducting Oxide Materials

Description: High-throughput combinatorial approaches have been used for the discovery and optimization of transparent conducting oxide (TCO) materials for PV applications. We report on current investigations in In-Zn-O, In-Ti-O and In-Mo-O systems. The InZnO system is shown to be amorphous in the best conducting range with a conductivity of ~ 3000 &#937;-cm-1 for 50%-70% In/Zn. The amorphous InZnO films are very smooth (2..ANG.. rms). In-Ti-O is found to be an excellent high-mobility TCO with mobilities of greater than 80 cm2/v-sec and conductivities of more than 6000 &#937;-cm-1 for sputtered thin film materials.
Date: November 1, 2005
Creator: Ginley, D. S.; van Hest, M. F. A. M.; Young, D.; Teplin, C. W.; Alleman, J. L.; Dabney, M. S. et al.
Partner: UNT Libraries Government Documents Department

Properties of Cd and Zn Partial Electrolyte Treated CIGS Solar Cells: Preprint

Description: We study the influence of Cd partial baths on the photovoltaic properties of CuInGaSe2 (CIGS) and CuIn-GaSSe2 (CIGSS) thin film absorbers. We find that efficient solar cells can be fabricated by this treatment, and we compare their properties with those containing CdS window layers grown by chemical bath deposition. The results suggest that Cd plays a dominant role in establishing efficient photovoltaic junctions in CuInSe2 alloys. Micron scale photoluminescence scans show non-uniformity along the length probed. Cd treatment quenches one of the luminescence transitions, which indicates a change in shallow acceptor level density. We present a model that helps to explain the evolution of photovoltaic action.
Date: May 1, 2002
Creator: Ramanathan, K.; Hasoon, F. S.; Smith, S.; Mascarenhas, A.; Al-Thani, H.; Alleman, J. et al.
Partner: UNT Libraries Government Documents Department

Highly Conductive Textured Molybdenum Doped Indium Oxide Thin Films

Description: We report on the pulsed laser deposition (PLD) of Mo-doped indium oxide (IMO) films with mobilities of up to 125 cm2/Vsec. Films have been grown from targets with 1-4 wt.% molybdenum. The optimum electrical and optical properties were obtained with the 2% target and yielded a maximum conductivity of 3717 S/cm with mobilities of 99 cm2/V-sec on (100) yttria stabilized zirconia (YSZ) single crystal substrates. Films also exhibit greater than 90% transparency in the visible range. Compared to commercial indium tin oxide (ITO) films, these PLD-grown IMO films have similar conductivity but since they have substantially higher mobility they have a correspondingly lower carrier concentration. The lower carrier concentration should extend the infrared window of the transparency for films of the same conductivity. This may lead to improved performance in a number of applications requiring improved performance TCOs.
Date: May 1, 2003
Creator: Warmsingh, C.; Yoshida, Y.; Readey, D.; Perkins, J.; Parilla, P.; Teplin, C. et al.
Partner: UNT Libraries Government Documents Department

The construction of a physical map for human chromosome 19

Description: Unlike a genetic map which provides information on the relative position of genes or markers based upon the frequency of genetic recombination, a physical map provides a topographical picture of DNA, i.e. distances in base pairs between landmarks. The landmarks may be genes, gene markers, anonymous sequences, or cloned DNA fragments. Perhaps the most useful type of physical map is one that consists of an overlapping set of cloned DNA fragments (contigs) that span the chromosome. Once genes are assigned to this contig map, sequencing of the genomic DNA can be prioritized to complete the most interesting regions first. While, in practice, complete coverage of a complex genome in recombinant clones may not be possible to achieve, many gaps in a clone map may be closed by using multiple cloning vectors or uncloned large DNA fragments such as those separated by electrophoretic methods. Human chromosome 19 contains about 60 million base pairs of DNA and represents about 2% of the haploid genome. Our initial interest in chromosome 19 originated from the presence of three DNA repair genes which we localized to a region of this chromosome. Our approach to constructing a physical map of human chromosome 19 involves four steps: building a foundation of overlapping cosmid contigs; bridging the gaps in the cosmid map with hybridization-based methods to walk onto DNA cloned in yeast and cosmids: orienting the contigs relative to each other and linking them to the cytological map; and coupling the contig map with the genetic map. The methods we use and the current status of the map are summarized in this report. 6 refs., 1 fig.
Date: November 5, 1990
Creator: Carrano, A.V.; Alleman, J.; Amemiya, C.; Ashworth, L.K.; Aslanidis, C.; Branscomb, E.W. et al.
Partner: UNT Libraries Government Documents Department

Combinatorial Optimization of Transparent Conducting Oxides (TCOS) for PV

Description: Transparent conducting oxides (TCOs) can serve a variety of important functions in thin-film photovoltaics such as transparent electrical contacts, antireflection coatings, and chemical barriers. Two areas of particular interest are TCOs that can be deposited at low temperatures and TCOs with high carrier mobilities. We have employed combinatorial high-throughput approaches to investigate both these areas. Conductivities of s = 2500 W-1-cm-1 have been obtained for In-Zn-O (IZO) films deposited at 100 C and s &gt; 5000 W-1-cm-1 for In-Ti-O (ITiO) and In-Mo-O (IMO) films deposited at 550 C. The highest mobility obtained was 83 cm2/V-s for ITiO deposited at 550 C.
Date: February 1, 2005
Creator: Perkins, J. D.; Taylor, M. P.; van Hest, M. F. A. M.; Teplin, C. W.; Alleman, J. L.; Dabney, M. S. et al.
Partner: UNT Libraries Government Documents Department