New Projects, Renewables

$6 million in awards to advance solar cell research

GOLDEN, COLO., APRIL 13, 2001 – The U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) today announced $6 million in awards to 11 universities and five companies for high tech research into non-conventional, photovoltaic technologies for creating electricity from sunlight.

Each award has the potential to create a breakthrough that could dramatically reduce the cost of solar electricity.

The awards will support fundamental and exploratory research to increase the amount of electricity produced by photovoltaic cells, reduce the cost of electricity produced, and ensure the cells performance over longer periods of time. The three-year awards from the fiscal year 2001 budget range from $160,000 to $500,000.

With the awards, the participating universities and companies will explore concepts that will make photovoltaic – or solar – cells cheaper and more efficient than those in use today. Higher efficiency means more electricity is produced from solar radiation by the solar cells. Some of the new concepts will explore entirely new methods, materials, and processes for creating electricity from sunlight. Two contracts, for instance, explore solar cells based on new plastic materials.

Universities in Arizona, California, Illinois, Iowa, Maryland, Michigan, New Jersey, and Ohio will receive the three-year awards, as will companies in California, Colorado, Delaware, and Michigan. Organizations receiving the awards are:

– University of Arizona, $499,000

– University of California, Santa Cruz, $323,000

– California Institute of Technology, $450,000

– California Institute of Technology, $346,000

– Unisun, $498,000

– United Innovations, Inc., $498,000

– ITN Energy Systems, Inc., $170,000 (one year)

– DuPont Central Research and Development, $495,000 (additional $376,000 provided by DuPont)

– University of Illinois, $355,000

– Iowa State University, $375,000

– Iowa State University, $160,000

– Johns Hopkins University, $463,000

– University of Michigan, $316,000

– United Solar Systems Corp, $500,000 (additional $500,000 provided by United Solar Systems Corp.)

– Princeton University, $391,000

– Ohio State University, $476,000

NREL is a national laboratory managed by Midwest Research Institute, Battelle and Bechtel. The lab is a leading center for research into photovoltaics, wind energy, plant- and waste-derived fuels, power and chemicals, energy-efficient buildings, advanced vehicle design, alternative fuels use and renewable hydrogen production, storage and use.



University of Arizona, Tucson, $499,000

Project Title: Liquid Crystal-Based Photovoltaic Technologies

Project Description: This project involves developing new solar electric devices based on self-assembling, discotic liquid crystalline (LC) organic layers having unique columnar ordering properties; air-stable, low work function cathodes; and high work function, chemically modified ITO (indium tin oxide) anodes. These liquid crystalline materials have a significant potential for solar electricity production because 1) they can be wet processed into large area panels; 2) their thin films, like polymers, can be “self-repairing” thereby minimizing defect sites and recombination centers; and 3) they exhibit the high charge mobilities seen in organic single crystals.


University of California, Santa Cruz, $323,000

Project Title: Polymer Hybrid Photovoltaics

Project Description: This project involves developing plastic or polymer-based photovoltaics that can have significant cost advantages over conventional technologies. This non-conventional solar electric technology would be compatible with liquid-based plastic processing and its devices could be assembled onto plastic substrates under atmospheric conditions using standard printing technologies, such as reel-to-reel and screen printing.

California Institute of Technology, Pasadena, $450,000

Project Title: Efficiency Improvements of Dye-Sensitized Nanocrystalline TiO2 Solar Cells

Project Description: This project involves better understanding of how to alter or replace the existing molecular components of the dye-sensitized nanocrystalline TiO2 (titanium dioxide – a material commonly found in many paint and toothpaste products) solar cell with materials that will simultaneously provide higher photovoltages while retaining high photocurrents so as to improve the efficiency of the nanocrystalline TiO2 solar cell.

California Institute of Technology, Pasadena, $346,000

Project Title: Layer Transfer Fabrication of High Efficiency Solar Cells

Project Description: This project involves the development of an ion implantation-induced layer transfer process and subsequent wafer bonding of dissimilar semiconductor materials. This approach offers the possibility of fabricating a nearly optimally-designed four junction III-V solar cell where the third cell, with approximately 1 eV energy gap, is made without the difficulties associated with epitaxial growth GaInNAs or BGaInAs. Such a cell could have an efficiency of 40 percent or greater.

Unisun, Newbury Park, $498,000 (small business)

Project Title: Non-Vacuum Processing of CIGS Solar Cells

Project Description: This project is aimed at demonstrating a non-vacuum process for fabricating high-efficiency thin-film CIGS (copper-indium-gallium-selenide) alloy solar cells. A non-vacuum process is potentially much cheaper than today’s vacuum processes. The specific objectives are to 1) achieve high-quality non-vacuum CIGS films by depositing well-packed planar particulate layers, improving control of the sintering of porous particulate layers into high-density films and by using graded alloys incorporating Ga and S; and 2) deposit high-transparency, high-conductance transparent conducting films at temperatures compatible with the underlying CIGS p-n junction.

United Innovations Inc., San Marcos, $498,000 (small business)

Project Title: Broad-Band Rugate Filters for High Performance Solar Electric Concentrators

Project Description: This subcontract involves the development of Rugate filters for use in a novel solar concentrator system for the generation of electricity. United Innovations Inc. is developing a dish concentrator system consisting of a first stage parabolic concentrator with circular heliostat facets, a second stage non-imaging concentrator, and a spherical cavity collecting the light and converting it to electricity using multiple III-V solar cells lining the interior surface of the cavity. The multiple III-V solar cells have different energy gaps with each cell covered by a Rugate filter with selective transmission/reflective characteristics permitting transmission of only the portion of the solar spectrum that matches the spectral response of the cell underneath. Ultimate projected cell and system level efficiencies for this concentrator concept are 50 percent and 38 percent respectively.


ITN Energy Systems Inc., Wheat Ridge, $170,000 (small business)

Project Title: Optical Rectenna Solar Cell

Project Description: This project involves a technical feasibility determination of a high efficiency, direct conversion device that converts available electromagnetic radiation (i.e. solar spectrum) directly into electric power. The device uses an antenna appropriate for solar spectrum frequencies and diode suitable for converting the high frequency power to usable power. The project is funded for one year to demonstrate the technical feasibility of the concept at a single wavelength of the solar spectrum.


DuPont Central Research and Development, Wilmington, $495,000 (additional $376,000 provided by DuPont)

Project Title: Development of a Solid-State Electrolyte for Dye-Sensitized Solar Cells

Project Description: This project involves research and development of a solid-state electrolyte for TiO2-based dye-sensitized solar cells and a study of the economic viability of the dye-sensitized solar cell. The replacement of the liquid electrolyte in today’s highest performing dye-sensitized solar cells offers several advantages for the technology. Candidate materials include gel ionomer systems, poly alkylcarbazoles, polythiophenes, polyanilines, poly alkylthiophenes and amine hole transport materials.


University of Illinois, Urbana, $355,000

Project Title: Low-Temperature Processing for CIGS Solar Cells

Project Description: This project involves the development of ionized physical vapor deposition (IPVD) as a low-temperature deposition method that would allow the fabrication of an upper Cu(In,Ga)Se2 (CIGS) device after completion of an underlying junction. Such a low-temperature deposition method is the most important enabling technology for the fabrication of multijunction CIGS devices with efficiencies exceeding 23 percent.


Iowa State University, Ames, $375,000

Project Title: Novel Group IV Materials for Photovoltaic Devices

Project Description: This project involves the development of new solar electric devices based on crystalline GeC alloy films prepared using remote, reactive plasma deposition with an ECR (electron cyclotron resonance) source. Group IV materials, germanium and carbon in this study, are those in the fourth column of the periodic table and include silicon, the material used in almost all of the world’s solar cells. Preliminary experimental results show promising optical absorption and band gaps for this new material system that are substantially better than those of silicon.

Iowa State University, Ames, $160,000

Project Title: Nanoscale Design of Thin-Film Heterogeneous Silicon Solar Cell Materials

Project Description: This project involves a theoretical study of the best performing hydrogenated silicon (a-Si:H) grown at the edge, that is the boundary, between amorphous and microcrystalline material deposition. This material, usually gown with H-dilution, has small cluster of nanocrystalline silicon embedded in an amorphous matrix. A related material, polymorphous silicon, is created from altered deposition conditions producing silicon clusters in the plasma and also consists of a heterogeneous mix of silicon clusters in an amorphous matrix. In the second part of this proposal, researchers will explore the potential of self-assembled nanocrystalline particles in a background amorphous matrix as a new solar cell material with optical characteristics better than those of amorphous silicon.


Johns Hopkins University, Baltimore, $463,000

Project Title: Solar Energy Conversion with Ordered, Molecular, Light Harvesting Arrays

Project Description: This project involves a novel approach to molecular solar cells and entails the use of linear chromophore rods that will be assembled into ordered, molecular, light harvesting arrays on electrode surfaces. The approach is new but borrows from lessons learned in dye-sensitized and “organic” solar cells and takes advantage of recent advances in synthetic chemistry that allow the rational construction of linear chromophore arrays.


University of Michigan, Ann Arbor, $316,000

Project Title: Synthesis and Nanometer-Scale Characterization of GaInNAs for High Efficiency Solar Cells

Project Description: This subcontract involves the development of new knowledge of GaInNAs and its properties for its use as a third junction in a 40 percent efficient multijunction solar cell. GaInNAs has several problems limiting its performance in solar cells, including low free carrier mobilities, significant alloy scattering, and significant free carrier compensation. A principal device performance limitation is the low quantum efficiency, which has been, attributed to short minority carrier diffusion lengths. Understanding the source of these limitations may lead to means to mitigate them.

United Solar Systems Corp., Troy, $500,000 (An additional $500,000 in funding provided by United Solar Systems Corp.)

Project Title: Microcrystalline Silicon Solar Cells

Project Description: This subcontract involves the development of microcrystalline silicon solar cells deposited at high rate using microwave glow discharge. Microcrystalline silicon material has been investigated for several years and no significant light induced degradation has been observed in microcrystalline silicon solar cells. But for cost-effective manufacturing, the deposition rate for microcrystalline silicon must be at least 10 times higher than that of a-SiGe alloy and still result in good photovoltaic characteristics.


Princeton University, Princeton, $391,000

Project Title: Double Heterostructure and Tandem Organic Solar Cells with Integrated Concentrators

Project Description: This subcontract involves the development of a novel light trapping molecular organic (i.e. non-polymeric) solar cell and improving its efficiency through thin film growth control, growth of multilayer structures, incorporation of phosphorescent dopants, and integration of optical collectors onto the cell substrate to trap solar radiation. This novel solar cell builds on the dramatic technological progress of the past decade in the field of organic light emitting devices used in commercially available emissive flat panel displays


Ohio State University, Columbus, $476,000

Project Title: GeSi Buffer Layers on Si Substrates for III-V Solar Cells

Project Description: This subcontract involves the development of novel, high-efficiency, multijunction single crystal III-V solar cells on lower cost, Si-based substrates via graded GeSi buffers. The work also could open the doors to new high efficiency cell design opportunities and advance the science behind integrating high efficiency cells with diverse and cheaper substrates well into the future.

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