High efficiency thin-film GaAs solar cells. First interim report, March 1--August 30, 1977 [electronic resource]
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Online Access |
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| Format: | Government Document Electronic eBook |
| Language: | English |
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Oak Ridge, Tenn. :
distributed by the Office of Scientific and Technical Information, U.S. Department of Energy,
1977.
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| Abstract: | The objective is to demonstrate the feasibility of producing high-efficiency (15% or greater) thin-film GaAs solar cells with costs suitable for terrestrial solar electric power generation. The approach is that of growing GaAs by organio-metallic chemical vapor deposition on recrystallized germanium (Ge) films previously deposited on metal substrates and fabricating AMOS (Antireflecting Metal-Oxide-Semiconductor) solar cells on the GaAs. Previously it had been determined that a water vapor-grown native oxide (temperature = 25/sup 0/C) was the most useful native oxide for AMOS cells. A new chemical surface preparation prior to oxide growth led to more uniform oxides and reduced interface contamination, yielding lower reverse saturation current densities, a near-unity diode ideality factor, and better reproducibility. Substituting silver (Ag) for gold metallization showed no change in starting cell efficiency, but did greatly improve high temperature stability of the AMOS solar cell. A new study was completed on antireflection coatings on AMOS GaAs solar cells, taking into account the spectral response of the cell and nature of the solar spectra, and the results submitted for publication. XPS (X-ray Photoelectron Spectroscopy) studies had found earlier that the more efficient native oxides had primarily As/sub 2/O/sub 3/ and Ga/sub 2/O/sub 3/ with little GaAsO/sub 4/. A new chemical step etching was developed which can be used to profile the oxide in 5- to 7-A/sup 0/ steps without modifying the oxide chemistry as does ion sputtering. A new Schottky barrier structure is described which can give cell efficiencies up to 16% without oxide interfacial layer effects and 20 to 22% with a moderate interfacial layer effect. AMOS solar cells fabricated on sliced polycrystalline GaAs wafers with 100- to 500-..mu..m grains using Sb/sub 2/O/sub 3/ deposited oxides showed 14% cell efficiency compared to 16.2% in a region with few grains. |
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| Item Description: | Published through SciTech Connect. 12/01/1977. "dst-1074-1" Stirn, R.J. Jet Propulsion Lab., Pasadena, CA (USA) |