Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Solar cell”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

InGaP Heterojunction Barrier Solar Cells

A new solar cell structure called a heterojunction barrier solar cell is described. As with previously reported quantum-well and quantum-dot solar cell structures, a layer of narrow band-gap material, such as GaAs or indium-rich InGaP, is inserted into the depletion region of a wide band-gap PN junction. Rather than being thin, however, the layer of narrow band-gap material is about 400-430 nm wide and forms a single, ultrawide well in the depletion region. Thin (e.g., 20-50 nm), wide band-gap InGaP barrier layers in the depletion region reduce the diode dark current. Engineering the electric field and barrier profile of the absorber layer, barrier layer, and p-type layer of the PN junction maximizes photogenerated carrier escape. This new twist on nanostructured solar cell design allows the separate optimization of current and voltage to maximize conversion efficiency.

Welser, Roger E.↗
NASA NTRS1981

Enhanced annealing of GaAs solar cell radiation damage

Solar cells are degraded by radiation damage in space. Investigations have been conducted concerning possibilities for annealing this radiation damage in GaAs solar cells, taking into account the conditions favoring such annealing. It has been found that continuous annealing as well as the combination of injection annealing with thermal annealing can lead to recovery from radiation damage under particularly favorable conditions in GaAs solar cells. The damage caused by both electrons and protons in GaAs solar cells can be substantially reduced by annealing at temperatures as low as 150 C, under appropriate conditions. This possibility makes the GaAs solar cells especially attractive for long space missions, or for missions in severe radiation environments. Attention is given to results concerning periodic thermal annealing, continuous annealing, and injection annealing combined with thermal annealing.

Loo, R.↗
NASA NTRS1984

Preflight study of San Marco D/L GaAs solar cell panels

The solar array for the San Marco D/L spacecraft is described and the performance of 4 GaAs solar cell panels are examined. In comparison to the typical Si solar cell panel for San Marco D/L, it is shown that each GaAs solar cell panel provides at least 23 percent more specific power at maximum output and 28 deg C. Also described here, are several measurements that will be made to evaluate the relative performance of Si and GaAs solar cell panels during the San Marco D/L flight.

Day, J. H., Jr.↗
NASA NTRS1976

The optimization of Ga (1-x)Al (x)As-GaAs solar cells for air mass zero operation and a study of Ga (1-x)Al (x)As-GaAs solar cells at high temperatures, phase 1

The three types of solar cells investigated were: (1) one consisting of a nGaAs substrate, a Zn doped pGaAs region, and a Zn doped Ga(1-x)Al(x)As layer, (2) one consisting of an nGaAs substrate, a Ge doped pGaAs region, and a pGa(1-x)Al(x)As upper layer, and (3) one consisting of an n+GaAs substrate, an nGa(1-x)Al(X)As region, a pGa(1-x)Bl(X) As region, and a pGa(1-y)Al(y)As upper layer. In all three cases, the upper alloy layer is thin and of high Al composition in order to obtain high spectral response over the widest possible range of photon energies. Spectral response, capacitance-voltage, current-voltage, diffusion length, sunlight (or the equivalent)-efficiency, and efficiency-temperature measurements were made as a function of device parameters in order to analyze and optimize the solar cell behavior.

Hovel, H. J.↗
NASA NTRS1975

V-grooved silicon solar cells

Silicon solar cells with macroscopic V-shaped grooves and microscopically texturized surfaces were made by preferential etching techniques. Various conditions for potassium hydroxide and hydrazine hydrate etching were investigated. Optical reflection losses from these surface were reduced. The reduced reflection occurred at all wavelengths and resulted in improved short circuit current and spectral response. Improved collection efficiency is also expected from this structure due to generation of carriers closer to the cell junction. Microscopic point measurements of collected current using a scanning electron microscope showed that current collected at the peaks of the texturized surface were only 80 percent of those collected in the valleys.

Baraona, C. R.↗
NASA NTRS1975

V-grooved silicon solar cells

Silicon solar cells with macroscopic V-shaped grooves and microscopically texturized surfaces have been made by preferential etching techniques. Various conditions for potassium hydroxide and hydrazine hydrate etching were investigated. Optical reflection losses from these surface were reduced. The reduced reflection occurred at all wavelengths and resulted in improved short circuit current and spectral response. Improved collection efficiency is also expected from this structure due to generation of carriers closer to the cell junction. Microscopic point measurements of collected current using a scanning electron microscope showed that current collected at the peaks of the texturized surface were only 80% of those collected in the valleys.

Baraona, C. R.↗
NASA NTRS1978

Glass tubes for protecting solar cells

Protecting solar cells against environmental effects is accomplished by putting them inside glass tubes instead of hermetically sealing them between pairs of flat glass sheets. If cells are coupled with storage battery integrated into tube, freestanding power source could be built.

Shelpuk, B.↗
NASA NTRS1978

Back wall solar cell

A solar cell is disclosed which comprises a first semiconductor material of one conductivity type with one face having the same conductivity type but more heavily doped to form a field region arranged to receive the radiant energy to be converted to electrical energy, and a layer of a second semiconductor material, preferably highly doped, of opposite conductivity type on the first semiconductor material adjacent the first semiconductor material at an interface remote from the heavily doped field region. Instead of the opposite conductivity layer, a metallic Schottky diode layer may be used, in which case no additional back contact is needed. A contact such as a gridded contact, previous to the radiant energy may be applied to the heavily doped field region of the more heavily doped, same conductivity material for its contact.

Brandhorst, H. W., Jr.↗
NASA NTRS1978

Ultraviolet irradiation at elevated temperatures and thermal cycling in vacuum of FEP-A covered silicon solar cells

Silicon solar cells covered with FEP-A were irradiated in vacuum with ultraviolet light and then subjected to thermal cycling. These accelerated laboratory conditions are believed to be equivalent to those experienced by FEP-A covered cells on the ATS-6 spacecraft and the results indicate a probable mechanism for the faster degradation of the FEP-A covered cells. Heat-bonded FEP-A covers apparently embrittle when exposed to four months of space UV radiation at elevated temperatures, and crack when subjected to thermal cycling during the eclipse period. Low energy proton radiation can then penetrate to the junction of the cell causing degradation of the open circuit voltage and maximum power to occur. An alternate method of application of FEP-A, such as with adhesives, may prevent such cracking.

Broder, J. D.↗
NASA NTRS1981

Annealing and anomalous high-energy electron irradiation effects in low-cost silicon N+P solar cells

Silicon solar cells of N(+)P type were subjected to 1 MeV electron irradiation (up to 10 to the 16th electrons/sq cm) and then annealed at 450 C for 20 min or annealed with no electron irradiation. Electron irradiation resulted in a degradation of longer wavelength cell response, but produced a marked enhancement of response at shorter wavelengths with a peak change of 40% at 0.44 microns. Subsequent thermal anneal at 450 C reduced the long-wavelength degradation, but enhancement at shorter wavelengths persisted. Excitation at the shorter wavelengths was in the N(+)-diffused layer and in the junction region of the cell. Anneal of unirradiated cells produced shorter-wavelength enhancement with a similar peaking at 0.44 microns, but with a relative change of only 20%. More enhancement was produced in the longer wavelength region (up to 0.8 microns). These effects in the different cell regions are explained by a decrease in the interstitial oxygen-impurity complexes (deep recombination levels) and the formation of substantial oxygen-silicon vacancy centers (donors).

Garlick, G. F. J.↗
NASA NTRS1984

18-percent efficient terrestrial silicon solar cells

Silicon solar cells are described which operate at energy conversion efficiencies in excess of 18 percent under standard terrestrial test conditions (AM1.5, 100 mW/sq cm, 28 C). These are believed to be the most efficient silicon cells reported to date. The high efficiency is a result of the combination of high open-circuit voltage due to the careful attention paid to passivation of the top surface of the cell; high fill factors due to the high open-circuit voltage and low parasitic resistance losses; and high short-circuit current due to the use of shallow diffusions, a low grid coverage, and an optimized double-layer antireflection coating.

Blakers, A. W.↗
NASA NTRS1984

High-efficiency silicon solar cells

Silicon solar cells are described which operate at energy conversion efficiencies independently measured at 18.7 percent under standard terrestrial test conditions (AM1.5, 100 mW/sq cm, 28 C). These are apparently the most efficient silicon cells fabricated to date. The high-efficiency results from a combination of high open-circuit voltage due to the careful attention paid to the passivation of the top surface of the cell, high fill factor due to the high open-circuit voltage and low parasitic resistance losses, and high short-circuit current density due to the use of shallow diffusions, a low grid coverage, and an optimized double layer antireflection coating.

Green, M. A.↗