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Tellurium-Containing Conjugated Materials for Solar Cells: From Sulfur to Tellurium

Description: A series of diketopyrrolopyrrole(DPP)-based small molecules have been synthesized by palladium-catalyzed coupling reactions. Electron-donating moieties (benzothiophene, benzoselenophene, and benzotellurophene) are bridged by an electron-withdrawing DPP unit to generate donor-acceptor-donor (D-A-D) type molecules. We observe red-shifts in absorption spectra of these compounds by varying heteroatoms from sulfur to tellurium. In bulk heterojunction solar cells with [6,6]phenyl-C61-butyric acid methyl ester (PC61BM) as acceptor, we obtain power conversion efficiencies of 2.4% (benzothiophene), 4.1% (benzoselenophene), and 3.0% (benzotellurophene), respectively.
Date: April 3, 2013
Creator: S., Park Y.; Kale, T.; Wu, Q.; Ocko, B.M. & Black, C.T., Grubbs, R.B.
Partner: UNT Libraries Government Documents Department

Nano-composite Structures for OPV Devices

Description: Improved material for use in organic photovoltaics (OPV) devices, also called polymer-solar cells (PSC), has been developed. Increased ordering of the active layer of bulk heterojunction (BHJ) cells has been achieved by the use of inert silica spheres in conjunction with suitable fullerene derivatives. Silica spheres with average diameters between 10 and 15 nm, consistent with the exciton diffusion length in the active layer, have been added. The potential for significantly improved device performance due to a higher degree of photon absorption, enabled by increased light scattering, and a maximized interface between electron donor and acceptor, ensuring efficient exciton dissociation, has been demonstrated. A method allowing for the covalent attachment of fullerene derivatives to the silica sphere surface has been developed.
Date: November 23, 2010
Creator: Richter, Henning
Partner: UNT Libraries Government Documents Department

Electrowetting Solar Cell

Description: This paper discusses the electrowetting solar cell. In comparison with traditional silicon-based PV solar cells, the electrowetting-based self-tracking technology will generate ~70% more green energy with a 50% cost reduction.
Date: April 19, 2012
Creator: Reilly, David & Cheng, Jiangtao
Partner: UNT Honors College

Review of Back Contact Silicon Solar Cells for Low-Cost Application

Description: Back contact solar cells hold significant promise for increased performance in photovoltaics for the near future. Two major advantages which these cells possess are a lack of grid shading loss and coplanar interconnection. Front contacted cells can have up to 10% shading loss when using screen printed metal grids. A front contact cell must also use solder connections which run from the front of one cell to the back of the next for series interconnection. This procedure is more difficult to automate than the case of co-planar contacts. The back contact cell design is not a recent concept. The earliest silicon solar cell developed by Bell Labs was a back contact device. There have been many design modifications to the basic concept over the years. To name a few, there is the Interdigitated Back Contact (IBC) cell, the Stanford Point contact solar cell, the Emitter Wrap Through (EWT), and its many variations. A number of these design concepts have demonstrated high efficiency. The SunPower back contact solar cell holds the efficiency record for silicon concentrator cells. The challenge is to produce a high efficiency cell at low cost using high throughput techniques. This has yet to be achieved with a back contact cell design. The focus of this paper will be to review the relevant features of back contact cells and progress made toward the goal of a low cost version of this device.
Date: August 4, 1999
Creator: Smith, David D.
Partner: UNT Libraries Government Documents Department

Advances in Photovoltaics at NREL

Description: This paper discusses the critical strategic research and development issues in the development of next-generation photovoltaic technologies, emphasizing thin-film technologies that are believed to ultimately lead to lower production costs. The critical research and development issues for each technology are identified. An attempt is made to identify the strengths and weaknesses of the different technologies, and to identify opportunities for fundamental research activities suited to advance the introduction of improved photovoltaic modules.
Date: September 9, 1999
Creator: von Roedern, Bolko
Partner: UNT Libraries Government Documents Department

CRADA Final Report: Process development for hybrid solar cells

Description: TCF funding of a CRADA between LBNL and RSLE leveraged RSLE's original $1M investment in LBNL research and led to development of a solar cell fabrication process that will bring the high efficiency, high voltage hybrid tandem solar cell closer to commercialization. RSLE has already built a pilot line at its Phoenix, Arizona site.
Date: February 14, 2011
Creator: Ager, Joel W.
Partner: UNT Libraries Government Documents Department

Process monitoring in solar cell manufacturing

Description: In this paper, the authors describe a new method that is capable of on-line monitoring of several solar cell process steps such as texturing, AR coatings, and metal contact properties. The measurement technique is rapid and specifically designed for solar cells and wafers. The system implementing this new concept is named ''PV Reflectometer.'' The idea was originally conceived several years ago and the principle of the method has been demonstrated for some simple cases. Recently, this method has been improved to be more suitable for commercial applications. For completeness, the paper first includes a brief review of the process control requirements and the common monitoring methods in solar cell production.
Date: October 26, 1999
Creator: Sopori, B.; Zhang, Y. & Chen, W.
Partner: UNT Libraries Government Documents Department

Amorphous and Microcrystalline Silicon Solar Cells: Preprint

Description: We review the progress made by amorphous silicon solar cells, including the emerging technology of solar cells of microcrystalline silicon. The long-term trend in the efficiency of stabilized laboratory cells based on a-Si:H has been a rise of {approx}0.6 % per year. The recent trend in the a-Si,Ge:H cell efficiency alone, measured in the spectral window assigned to the bottom device in a triple-junction cell, has been an increase of {approx}0.16% per year. These improvements have brought within reach the target of 15% efficiency identified by EPRI and DOE for widespread application. Our review leads to an identification of areas of promising research, with emphasis on the fundamental science required to reach the 15% target, and then to move to the next-level efficiency goal.
Date: April 1, 1999
Creator: Wagner, S. (Princeton University); Carlson, D. E. (Solarex) & Branz, H. M. (National Renewable Energy Laboratory)
Partner: UNT Libraries Government Documents Department

Exploration of GaInT1P and Related T1-Containing III-V Alloys for Photovoltaics

Description: This paper discusses the results of an attempt to grow GaInTlP for application as a 1-eV material for the third junction of a GaInP/GaAs/3rd-junction high-efficiency solar cell. Although early indications from the literature were promising, we are unable to produce crystalline homogeneous material, and so we conclude that this material is not a promising candidate for such applications as photovoltaics.
Date: November 2, 1998
Creator: Friedman, D.J.; Kibbler, A.E. & Kurtz, S.R.
Partner: UNT Libraries Government Documents Department

Development of A Thin Film Crystalline Silicon Solar Cell

Description: A new design for a single junction, thin film Si solar cell is presented. The cell design is compatible with low-temperature processing required for the use of a low-cost glass substrate, and includes effective light trapping and impurity gettering. Elements of essential process steps are discussed.
Date: November 19, 1998
Creator: Sopori, B.; Chen, W. & Zhang, Y.
Partner: UNT Libraries Government Documents Department

Deep Levels in p- and n-type InGaAsN for High Efficiency Multi-Junction III-V Solar Cells

Description: Red Teaming is an advanced form of assessment that can be used to identify weaknesses in a variety of cyber systems. it is especially beneficial when the target system is still in development when designers can readily affect improvements. This paper discusses the red team analysis process and the author's experiences applying this process to five selected Information Technology Office (ITO) projects. Some detail of the overall methodology, summary results from the five projects, and lessons learned are contained within this paper.
Date: November 11, 1999
Creator: ALLERMAN,ANDREW A.; JONES,ERIC D.; KAPLAR,ROBERT J.; KURTZ,STEVEN R.; KWON,DAEWON & RINGEL,STEVEN A.
Partner: UNT Libraries Government Documents Department

Substitution Effects of Phenothiazine and Porphyrin Dyes in Dye-sensitized Solar Cells

Description: The details of dye sensitized solar cells was explained and phenothiazine and porphyrin based dyes were synthesized for use in DSSCs. DSSCs offer a unique and cost effective method of renewable energy. DSSCs are characterized through various tests, with the overall efficiency, η, bearing the greatest importance. Incident photon to current conversion efficiency, or IPCE, is also another important characterization of DSSCs. Effect of positioning of the cyanoacrylic acid anchoring group on ring periphery of phenothiazine dye on the performance of dye sensitized solar cells (DSSCs) is reported. The performances of the cells are found to be prominent for solar cells made out of Type-1 dyes compared to Type-2 dyes. This trend has been rationalized based on spectral, electrochemical, computational and electrochemical impedance spectroscopy results. Free-base and zinc porphyrins bearing a carboxyl anchoring group at the para, meta, or ortho positions of one of the meso-phenyl rings were synthesized for DSSCs. Photoelectrochemical studies were performed after immobilization of porphyrins onto nanocrystalline TiO2. The performance of DSSCs with the porphyrin anchoring at the para or meta position were found to greatly exceed those in the ortho position. Additionally, zinc porphyrin derivatives outperformed the free-base porphyrin analogs, including better dye regeneration efficiency for the zinc porphyrin derivatives and for the meta and para derivatives through electrochemical impedance spectroscopy studies. The overall structure-performance trends observed for the present porphyrin DSSCs have been rationalized based on spectral, electrochemical, electrochemical impedance spectroscopy and transient spectroscopy results.
Date: December 2013
Creator: Hart, Aaron S.
Partner: UNT Libraries

Optimization of processing and modeling issues for thin film solar cell devices: Final report, February 3, 1997--September 1, 1998

Description: This final report describes results achieved under a 20-month NREL subcontract to develop and understand thin-film solar cell technology associated to CuInSe{sub 2} and related alloys, a-Si and its alloys, and CdTe. Modules based on all these thin films are promising candidates to meet DOE's long-range efficiency, reliability and manufacturing cost goals. The critical issues being addressed under this program are intended to provide the science and engineering basis for the development of viable commercial processes and to improve module performance. The generic research issues addressed are: (1) quantitative analysis of processing steps to provide information for efficient commercial-scale equipment design and operation; (2) device characterization relating the device performance to materials properties and process conditions; (3) development of alloy materials with different bandgaps to allow improved device structures for stability and compatibility with module design; (4) development and improved window/heterojunction layers and contacts to improve device performance and reliability; and (5) evaluation of cell stability with respect to device structure and module encapsulation.
Date: February 28, 2000
Creator: Birkmire, R. W.; Phillips, J. E.; Shafarman, W. N.; Hegedus, S. S. & McCandless, B. E.
Partner: UNT Libraries Government Documents Department

Optimization of Processing and Modeling Issues for Thin Film Solar Cell Devices Including Concepts for The Development of Polycrystalline Multijunctions: Annual Report; 24 August 1998-23 August 1999

Description: This report describes results achieved during phase 1 of a three-phase subcontract to develop and understand thin-film solar cell technology associated to CuInSe{sub 2} and related alloys, a-Si and its alloys, and CdTe. Modules based on all these thin films are promising candidates to meet DOE long-range efficiency, reliability, and manufacturing cost goals. The critical issues being addressed under this program are intended to provide the science and engineering basis for the development of viable commercial processes and to improve module performance. The generic research issues addressed are: (1) quantitative analysis of processing steps to provide information for efficient commercial-scale equipment design and operation; (2) device characterization relating the device performance to materials properties and process conditions; (3) development of alloy materials with different bandgaps to allow improved device structures for stability and compatibility with module design; (4) development of improved window/heterojunction layers and contacts to improve device performance and reliability; and (5) evaluation of cell stability with respect to illumination, temperature, and ambient and with respect to device structure and module encapsulation.
Date: August 25, 2000
Creator: Birkmire, R.W.; Phillips, J.E.; Shafarman, W.N.; Eser, E.; Hegedus, S.S. & McCandless, B.E. (Institute of Energy Conversion)
Partner: UNT Libraries Government Documents Department

Light-trapped, interconnected, Silicon-Film{trademark} modules. Final technical status report

Description: AstroPower has continued its development of an advanced thin-silicon-based photovoltaic module product. This module combines the performance advantages of thin light-trapped silicon layers with the capability of integration into a low-cost, monolithically interconnected module. This report summarized work carried out over a 3-year, cost-shared contract. Key results accomplished during this phase include an NREL-verified conversion efficiency of 12.5% on a 0.47-cm{sup 2} device. The device structure used an insulating substrate and an active layer less than 100 {micro}m thick. A new metalization scheme was designed using insulating crossovers. This technology was demonstrated on a 36-segment, 321-cm{sup 2}, interconnected module. That module was tested at NREL with an efficiency of 9.79%. Further advances in metalization have led to an advanced single back-contact design that will offer low cost through ease of processing and higher performance through reduced shading.
Date: April 1, 1998
Creator: Hall, R.B.; Rand, J.A.; Ford, D.H. & Ingram, A.E.
Partner: UNT Libraries Government Documents Department

The results of the PEP`93 intercomparison of reference cell calibrations and newer technology performance measurements: Final report

Description: This report presents the results of an international intercomparison of photovoltaic (PV) performance measurements and calibrations that took place from 1993 to 1997. The intercomparison, which was organized and operated by a group of representatives from national PV measurements laboratories, was accomplished by circulating two sample sets. One set, consisting of 20 silicon reference cells, was intended to form the basis of an international PV reference scale. A qualification procedure applied to the calibration results gave average calibration numbers with an overall standard deviation of less than 2% for the entire set. The second sample set was assembled from a wide range of newer technologies that present unique problems for PV measurements. As might be expected, these results showed much greater differences among the laboratories. Methods were then identified that should be used to measure such devices, along with problems to avoid. The report concludes with recommendations for future intercomparisons.
Date: March 1, 1998
Creator: Osterwald, C.R.; Anevsky, S. & Barua, A.K.
Partner: UNT Libraries Government Documents Department

Simplified module assembly using back-contact crystalline-silicon solar cells

Description: The authors are developing new module concepts that encapsulate and electrically connect all the crystalline-silicon (c-Si) photovoltaic (PV) cells in a module in a single step. The new assembly process (1) uses back-contact c-Si cells, (2) uses a module backplane that has both the electrical circuit, encapsulant, and backsheet in a single piece, and (3) uses a single-step process for assembly of these components into a module. This new process reduces module assembly cost by using planar processes that are easy to automate, by reducing the number of steps, and by eliminating low-throughput (e.g., individual cell tabbing, cell stringing, etc.) steps. The authors refer to this process as monolithic module assembly since it translates many of the advantages of monolithic module construction of thin-film PV modules to wafered c-Si PV modules. Preliminary development of the new module assembly process, and some estimations of the cost potential of the new process, are presented.
Date: November 1, 1997
Creator: Gee, J.M.; Garrett, S.E. & Morgan, W.P.
Partner: UNT Libraries Government Documents Department

Reactive Ion Etching for Randomly Distributed Texturing of Multicrystalline Silicon Solar Cells

Description: The quality of low-cost multicrystalline silicon (mc-Si) has improved to the point that it forms approximately 50% of the worldwide photovoltaic (PV) power production. The performance of commercial mc-Si solar cells still lags behind c-Si due in part to the inability to texture it effectively and inexpensively. Surface texturing of mc-Si has been an active field of research. Several techniques including anodic etching [1], wet acidic etching [2], lithographic patterning [3], and mechanical texturing [4] have been investigated with varying degrees of success. To date, a cost-effective technique has not emerged.
Date: May 1, 2002
Creator: ZAIDI, SALEEM H
Partner: UNT Libraries Government Documents Department

Fundamental Understanding and Development of Low-Cost, High-Efficient Silicon Solar Cells Final Progress Report: Sept. 1999 - June 2000

Description: The overall objectives of this program are to (1) develop rapid and low-cost processes for manufacturing that can improve yield, throughput, and performance of silicon photovoltaic devices, (2) design and fabricate high-efficiency solar cells on promising low-cost materials, and (3) improve the fundamental understanding of advanced photovoltaic devices. Several rapid and potentially low-cost technologies are described in this report that were developed and applied toward the fabrication of high-efficiency silicon solar cells.
Date: February 1, 2001
Creator: ROHATGI, A.; EBNG, A.; YELUNDUR, V.; HILALI, M.; JEONG, J.; PREGELJ, A. et al.
Partner: UNT Libraries Government Documents Department

Plasma Texturing of Silicon Solar Cells

Description: Surface texture promotes enhanced light absorption in Si solar cells. The quality of lower cost multicrystalline-silicon (mc-Si) has increased to the point that its cell performance is close to that of single c-Si cells, with the major difference resulting from the inability to texture mc-Si affordably. This has reduced the cost-per-watt advantage of mc-Si. Surface texturing aimed at enhanced absorption in Si has been historically obtained by creating multimicrometer-sized pyramids using anisotropic wet etchants on single-crystalline silicon that take advantage of its single crystalline orientation. Since the surface feature sizes are several times the length of the incident solar wavelengths involved, the optical analysis of the reflected and absorbed light can be understood using geometrical optics. Geometrical textures reduce reflection and improve absorption by double-bounce and oblique light coupling into the semiconductor. However, geometrical texturing suffers from several disadvantages that limit its effectiveness. Some of these are listed below: (a) Wet-chemical anisotropic etching used to form random pyramids on <100> crystal orientation is not effective in the texturing of low-cost multicrystalline wafers, (b) Anti-reflection films deposited on random features to reduce reflection have a resonant structure limiting their effectiveness to a narrow range of angles and wavelengths. Various forms of surface texturing have been applied to mc-Si in research, including laser-structuring, mechanical grinding, porous-Si etching, and photolithographically defined etching. However, these may be too costly to ever be used in large-scale production. A Japanese firm has reported the development of an RIE process using Cl{sub 2} gas, which textures multiple wafers per batch, making it attractive for mass-production [1]. Using this process, they have produced a 17.1% efficient 225-cm{sup 2} mc-Si cell, which is the highest efficiency mc-Si cell of its size ever reported. This proves that RIE texturing does not cause performance-limiting damage to Si cells. In this paper, ...
Date: July 20, 1999
Creator: Narayanan, Mohan; Roy, Madhu; Ruby, Douglas S. & Zaidi, Saleem H.
Partner: UNT Libraries Government Documents Department

Advanced Silicon Space Solar Cells Using Nanotechnology

Description: Application of nanotechnology and advanced optical structures offer new possibilities for improved radiation tolerance in silicon solar cells. We describe the application of subwavelength diffractive structures to enhance optical absorption near the surface, and thereby improve the radiation tolerance.
Date: March 31, 1999
Creator: Gee, J.M.; Ruby, D.S. & Zaidi, S.H.
Partner: UNT Libraries Government Documents Department

Acceptor-sensitizers for Nanostructured Oxide Semiconductor in Excitonic Solar Cells

Description: Organic dyes are examined in photoelectrochemical systems wherein they engage in thermal (rather than photoexcited) electron donation into metal oxide semiconductors. These studies are intended to elucidate fundamental parameters of electron transfer in photoelectrochemical cells. Development of novel methods for the structure/property tuning of electroactive dyes and the preparation of nanostructured semiconductors have also been discovered in the course of the presented work. Acceptor sensitized polymer oxide solar cell devices were assembled and the impact of the acceptor dyes were studied. The optoelectronic tuning of boron-chelated azadipyrromethene dyes has been explored by the substitution of carbon substituents in place of fluoride atoms at boron. Stability of singlet exited state and level of reduction potential of these series of aza-BODIPY coumpounds were studied in order to employ them as electron-accepting sensitizers in solid state dye sensitized solar cells.
Date: August 2014
Creator: Berhe, Seare Ahferom
Partner: UNT Libraries