Engineering topics

Brinker, D. J.

Publications and source records attributed to Brinker, D. J..

29 records · Page 2

NASA NTRS1990

Peeled film GaAs solar cell development

Thin-film, single-crystal gallium arsenide (GaAs) solar cells could exhibit a specific power approaching 700 W/kg including coverglass. A simple process has been described whereby epitaxial GaAs layers are peeled from a reusable substrate. This process takes advantage of the extreme selectivity of the etching rate of aluminum arsenide (AlAs) over GaAs in dilute hydrofluoric acid. The feasibility of using the peeled film technique to fabricate high-efficiency, low-mass GaAs solar cells is presently demonstrated. A peeled film GaAs solar cell was successfully produced. The device, although fractured and missing the aluminum gallium arsenide window and antireflective coating, had a Voc of 874 mV and a fill factor of 68 percent under AM0 illumination.

Wilt, D. M.↗

NASA NTRS1990

High altitude AM0 testing of PV concentrator lens elements

Recently, the NASA Lewis Research Center modified its Lear High Altitude Test Facility to fly two prototype ENTECH minidome Fresnel lens photovoltaic concentrator elements. The tests were highly successful, and the results verified the ability of the Lear High Altitude Facility to measure the optical performance of individual concentrator lens elements and concentrator/cell combinations at near AM0 insolation conditions. The two concentrator lenses flown achieved optical efficiencies, based on a gallium arsenide concentrator cell response, of 89.8 percent and 90.0 percent. The flights demonstrated the ability of the aircraft to maintain the pointing accuracy required to obtain useful data. With proper alignment of the collimating tube and the pilot's sunsight, this facility could easily maintain a pointing accuracy of + or - 0.5 deg for a sufficiently long time to obtain accurate, reproducible results.

Piszczor, M. F.↗

NASA NTRS1990

Effects of radiation of InP cells epitaxially grown on Si and GaAs substrates

The properties of heteroepitaxial InP cells were determined both before and after 10-MeV proton irradiations. Numerical values, obtained for the diffusion and recombination components of the reverse saturation currents, were found to be consistent with the distribution of dislocations. The radiation resistance of the heteroepitaxial cells was significantly greater than that observed for n/p homoepitaxial InP cells. The carrier removal rate, obtained by C-V measurements, was 1800/cm for 10-MeV protons compared with 2.2/cm for 1-MeV electrons. The high carrier removal rate was found to have no significant effect on the cell's series resistance. It was concluded that the heteroepitaxial cell performance is dominated by the high dislocation density attributable to lattice constant mismatch. Although the efficiencies of the present cells are low, the recent achievement of 13.7 percent AM0 efficiencies using a GaAs substrate demonstrates the marked improvement that can be attained using more appropriate transition layers.

Weinberg, I.↗

NASA NTRS1990

Lightweight concentrator module with 30 percent AM0 efficient GaAs/GaSb tandem cells

A concept is presented for an aerospace concentrator module with lightweight domed lenses and 30 percent AM0 efficient GaAs/GaSb tandem solar cell circuits. The performance of transparent GaAs cells is reviewed. NASA's high-altitude jet flight calibration data for recent GaSb cells assembled with bulk GaAs filters are reported, along with subsequent Boeing and NASA measurements of GaSb I-V performance at various light levels and temperatures. The expected performance of a basic two-terminal tandem concentrator circuit with three-to-one voltage matching is discussed. All of the necessary components being developed to assemble complete flight test coupons are shown. Straightforward interconnect and assembly techniques yield voltage matched circuits with near-optimum performance over a wide temperature range.

Avery, J. E.↗

NASA NTRS1990

23.5 percent thin-film space concentrator cells

Thin-film AlGaAs-GaAs double-heterostructure concentrator cells were fabricated which exhibit total-area conversion efficiencies as high as 23.5 percent AM0 at 100 suns, 25 C. This is one of the best space concentrators measured to date at NASA and is designed for a thin-film cell without a prismatic coverglass. This solar cell structure consists of a GaAs/AlGaAs film less than 5 micron thick mounted to a glass cover/superstrate, with coplanar back-side contacts. The coverglass is not prismatic. The CLEFT process, a method for mechanically separating epitaxial layers from their substrate, is used to process these cells into thin films. The advantages of single-crystal GaAs are thereby retained, while reducing weight and cutting cost by allowing for substrate reuse. Thin-film cells also have better thermal management capabilities and can be stacked for use in tandem structures. Cell fabrication and performance are described, and directions for further improvements are identified.

Dingle, B. D.↗

NASA NTRS1989

Thermal annealing of GaAs concentrator solar cells

The thermal annealing of GaAs concentrator cells after electron irradiation is reported. Results are given for cells annealed at 150, 200, and 250 C. Isochronal annealing was done for 20 min intervals up to 350 C. For cells irradiated with electrons of energies between 0.7 and 2.3 MeV, the recovery decreases with increasing electron energy. Isothermal and isochronal annealing produce the same recovery. Cells irradiated to 3 x 10 to the 15th or 1 x 10 to the 16th e/sq cm recover to similar unannealed fractions. Significant annealing is seen starting at 150 C, although very long times are required.

Curtis, H. B.↗

NASA NTRS1988

Progress in InP solar cell research

Progress, in the past year, in InP solar cell research is reviewed. Small area cells with AMO, total area efficiencies of 18.8 percent were produced by OMCVD and Ion Implantation. Larger area cells (2 and 4 sq cm) were processed on a production basis. One thousand of the 2 sq cm cells will be used to supply power to a small piggyback lunar orbiter scheduled for launch in February 1990. Laboratory tests of ITO/InP cells, under 10 MeV proton irradiation, indicate radiation resistance comparable to InP n/P homojunction cells. Computer modeling studies indicate that, for identical geometries and dopant concentrations, InP solar cells are significantly more radiation resistant than GaAs under 1 MeV electron irradiation. Additional computer modeling calculations were used to produce rectangular and circular InP concentrator cell designs for both the low concentration SLATS and higher concentration Cassegrainian Concentrators.

Weinberg, I.↗

NASA NTRS1986

Indium phosphide solar cells: status and prospects for use in space

The current status of indium phosphide cell research is reviewed and state of the art efficiencies compared to those of GaAs and Si. It is shown that the radiation resistance of InP cells is superior to that of either GaAs or Si under 1 MeV electron and 10 MeV proton irradiation. Using lightweight blanket technology, a SEP array structure and projected cell efficiencies, array specific powers are obtained for all three cell types. Array performance is calculated as a function of time in orbit. The results indicate that arrays using InP cells can outperform those using GaAs or Si in orbits where radiation is a significant cell degradation factor. It is concluded that InP solar cells are excellent prospects for future use in the space radiation environment.

Weinberg, I.↗

NASA NTRS1986

Indium phosphide solar cells - Status and prospects for use in space

Weinberg, I.↗

NASA NTRS1984

GaAs and 3-5 compound solar cells status and prospects for use in space

Gallium arsenide solar cells equal or supass the best silicon solar cells in efficiency, radiation resistance, annealability, and in the capability to produce usable power output at elevated temperatures. NASA has been involved in a long range research and development program to capitalize on these manifold advantages, and to explore alternative III-V compounds for additional potential improvements. The current status and future prospects for research and development in this area are reviewed and the progress being made toward development of GaAs cells suitable for variety of space missions is discussed. Cell types under various stages of development include n(+)/p shallow homojunction thin film GaAs cells, x100 concentration ratio p/n and n/p GaAs small area concentrator cells, mechanically-stacked, two-junction tandem cells, and three-junction monolithic cascade cells, among various other cell types.

Flood, D. J.↗

NASA NTRS1982

Radiation damage and annealing in large area n+/p/p+ GaAs shallow homojunction solar cells

Annealing of radiation damage was observed for the first time in VPE-grown, 2- by 2-cm, n+/p/p+ GaAs shallow homojunction solar cells. Electrical performance of several cells was determined as a function of 1-MeV electron fluence in the range of 10 to the 13th power to 10 to the 15th power e-/sq cm and as a function of thermal annealing time at various temperatures. Degradation of normalized power output after a fluence of 10 to the 15th power 1-MeV electrons/sq cm ranged from a low of 24 to 31 percent of initial maximum power. Normalized short circuit current degradation was limited to the range from 10 to 19 percent of preirradiated values. Thermal annealing was carried out in a flowing nitrogen gas ambient, with annealing temperatures spanning the range from 125 to 200 C. Substantial recovery of short circuit current was observed at temperatures as low as 175 C. In one case improvement by as much as 10 percent of the postirradiated value was observed. The key features of these cells are their extremely thin emitter layers (approxmately 0.05 micrometers), the absence of any Al sub xGd sub 1-x As passivating window layer, and their fabrication by vapor phase epitaxy.

Flood, D. J.↗