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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.

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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

M-I-S solar cell - Theory and experimental results

The paper presents an operating-mode analysis of an MIS solar cell and discusses the advantages which can arise as a result of the use of transport control, field shaping (increased n factor), and zero bias barrier height modification. It is noted that for an n-type semiconductor, it is relatively easy to obtain an enhanced n factor using acceptor-like states without an increase in diode saturation current, the converse being true for p-type semiconductors. Several MIS configurations are examined: an acceptor-like, localized state configuration producing field shaping and no change in diode saturation current, and acceptor-like localized configurations producing field shaping, with a decrease of diode saturation current, in one case, and an increase in the other.

Childs, R.↗
NASA NTRS1976

Fabrication of OSOS cells by neutral ion beam sputtering

Oxide semiconductor on silicon (OSOS) solar cells have been fabricated from various indium tin oxide (In2O3)x(SnO2)1-x compositions sputtered onto p-type single crystal silicon substrates with a neutralized argon ion beam. High temperature processing or annealing was not required. The highest efficiency was achieved with x = 0.91 and was 12 percent. The cells are environmentally rugged, chemically stable, and show promise for still higher efficiencies. Moreover, the ion beam sputtering fabrication technique is amenable to low cost, continuous processing.

Burk, D. E.↗
NASA NTRS1980

CdInP semiconductor alloy

Semiconductor alloy of CdSInP deposited onto CdS substrate using liquid-phase epitaxy (LPE) employed in solvent is replacement for InP n- and p-type heterojunction layers contained in GaAsp laser devices. Alloy will aid in lowering current density of laser and enhance its longevity and CW operation at room temperature.

Hawrylo, F. Z.↗
NASA NTRS1979

Method for fabricating solar cells having integrated collector grids

A heterojunction or Schottky barrier photovoltaic device comprising a conductive base metal layer compatible with and coating predominately the exposed surface of the p-type substrate of the device such that a back surface field region is formed at the interface between the device and the base metal layer, a transparent, conductive mixed metal oxide layer in integral contact with the n-type layer of the heterojunction or Schottky barrier device having a metal alloy grid network of the same metal elements of the oxide constituents of the mixed metal oxide layer embedded in the mixed metal oxide layer, an insulating layer which prevents electrical contact between the conductive metal base layer and the transparent, conductive metal oxide layer, and a metal contact means covering the insulating layer and in intimate contact with the metal grid network embedded in the transparent, conductive oxide layer for conducting electrons generated by the photovoltaic process from the device.

Evans, J. C., Jr.↗
NASA NTRS1978

Development of Low Cost Contacts to Silicon Solar Cells

Commercial electroless Cu solutions were used. Satisfactory adhesion (and fairly good cell performance) resulted from the use of thin layers of barrier metals such as Au, Cr or Pd. In these tests, photoresist masks were used to contact silicon P-type slices with diffused N+ and alloyed P+ surfaces; and electrolytic Cu solution was used to build up the contact thickness to provide good cell behavior. In addition some cells with evaporated Cr-Cu contacts were also made (along with evaporated Ti-Pd-Ag contacts as controls), with the intention of subjecting cells to gradually increasing heat-treatments, to determine whether Cu causes the cells to be inherently unstable.

Iles, P. A.↗
NASA NTRS1979

The Establishment of a Production-ready Manufacturing Process Utilizing Thin Silicon Substrates for Solar Cells

During the months of February and March, work towards the goals of the contract were started as scheduled. The first shipment of thin substrates were received and wafer processing was initiated. The objective of the contract is to investigate, develop and characterize the methods for establishing a production-ready manufacturing process which utilizes thin silicon substrates for solar cells. The thin substrates to be manufactured are three inches diameter, p-type Czochralski wafers of approximately 1 Omega cm resistivity. The wafers are prepared by sawing directly to thickness of 8 mils and 5 mils. To ensure removal of residual saw damage, most substrates are chemically etched to final thicknesses of 7 mils and 4 mils. The thin substrates are used to fabricate solar cells by standard processing techniques.

Pryor, R. A.↗
NASA NTRS1979

Automated Array Assembly, Phase 2

The large scale production of silicon solar cell array panels is discussed. The cost and performance of three manufacturing sequences designed to convert silicon sheet and wafers into solar panels is analyzed. The production of ion implanted and furnace annealed solar cells made using solar grade n- and p-type wafers is examined. The performance of production size lots is examined with regard to the relationship between the ion implant and furnace anneal parameters and the ability to form consistently good thick film screen printed contacts. The spray on antireflection coating process is evaluated. The performance of several lots of cells before and after coating is measured. The structure and refractive index of the RCA I (TiO2) coating is compared with commercial solutions. Sensitivity of coated, screen printed cells to the post heat treatment required to cure the films is assessed.

Daiello, R. V.↗
NASA NTRS1979

Modeling of thin, back-wall silicon solar cells

The performance of silicon solar cells with p-n junctions on the nonilluminated surface (i.e., upside-down or back-wall cells) was calculated. These structures consisted of a uniformly shaped p-type substrate layer, a p(+)-type field layer on the front (illuminated) surface, and a shallow, n-type junction on the back (nonilluminated) surface. A four-layer solar cell model was used to calculate efficiency, open-circuit voltage, and short-circuit current. The effect on performance of p-layer thickness and resistivity was determined. The diffusion length was varied to simulate the effect of radiation damage. The results show that peak initial efficiencies greater than 15 percent are possible for cell thicknesses or 100 micrometers or less. After 10 years of radiation damage in geosynchronous orbit, thin (25 to 50 micrometers thick) cells made from 10 to 100 ohm cm material show the smallest decrease (approximately 10 percent) in performance.

Baraona, C. R.↗
NASA NTRS1979

Annealing of radiation damage in 0.1- and 2-ohm-centimeter Silicon solar cells

Isochronal and isothermal annealing studies were conducted on 0.1 and 2 ohm centimeter n(+)/p silicon cells after irradiation by 1 MeV electrons at fluences of 10 to the 14th power, 5 times 10 to the 14th power, and 10 to the 15th power per square centimeter. For the 0.1 ohm centimeter cells, reverse annealing was not observed in the isochronal data. However, reverse annealing was observed between approximately 200 and 325 C in the isochronal data of the 2 ohm centimeter cells. Isothermal annealing of 0.1 ohm centimeter cells at 500 C restored pre-irradiation maximum power P sub max within 20 minutes at fluence = 10 to the 14th power, in 180 minutes at fluence = 5 times 10 to the 14th power and to 92 percent of pre-irradiation P sub max in 180 minutes for fluence = 10 to the 15th power. Annealing at 450 C was found inadequate to restore 0.1 ohm centimeter cell performance within reasonable times for all fluence levels. By comparison, at 450 C, the P sub max of 2 ohm centimeter cells was restored within 45 minutes, for the two highest fluence levels, while for the lowest fluence, restoration was completed within 15 minutes. Spectral response data indicate that, for both resistivities, degradation occurs predominantly in the cells p-type base region.

Weinberg, I.↗
NASA NTRS1978

Photoelectrolysis of water at high current density - Use of laser light excitation of semiconductor-based photoelectrochemical cells

In the present paper, some results are given for UV laser light irradiation of the photoanode (SnO2, SrTiO3, or TiO2) in a cell for the light-driven electrolysis of H2O, at radiation intensities of up to 380 W/sq cm. The properties of the anode material are found to be independent of light intensity. Conversion of UV light to stored chemical energy in the form of 2H2/O2 from H2O was driven at a rate of up to 30 W/sq cm. High O2 evolution rates at the irradiated anodes without changes in the current-voltage curves are attributed to the excess oxidizing power associated with photogenerated holes. A test for this sort of hypothesis for H2 evolution at p-type materials is proposed.

Wrighton, M. S.↗
NASA NTRS1979

Titanium in silicon as a deep level impurity

Titanium inserted in silicon by diffusion or during Czochralski ingot growth is electrically active to a concentration level of about 4 x 10 to the 14th per cu cm. It is reported that Hall measurements after diffusion show conversion of lightly doped p-type Si to n-type due to a Ti donor level at E sub c -0.22 eV. In addition, in DLTS measurements of n(+)p structures this level shows as an electron (minority carrier) trap at E sub c -0.26 eV with an electron capture cross section of about 3 x 10 to the -15th per sq cm at 300 K. Finally, a Ti electrically active concentration of about 1.35 x 10 to the 13th per cu cm in p type Si results in a minority carrier (electron) lifetime of 50 nsec at 300 K.

Chen, J.-W.↗
NASA NTRS1980

Radiation damage in high voltage silicon solar cells

Three high open-circuit voltage cell designs based on 0.1 ohm-cm p-type silicon were irradiated with 1 MeV electrons and their performance determined to fluences as high as 10 to the 15th power/sq cm. Of the three cell designs, radiation induced degradation was greatest in the high-low emitter (HLE cell). The diffused and ion implanted cells degraded approximately equally but less than the HLE cell. Degradation was greatest in an HLE cell exposed to X-rays before electron irradiation. The cell regions controlling both short-circuit current and open-circuit voltage degradation were defined in all three cell types. An increase in front surface recombination velocity accompanied time dependent degradation of an HLE cell after X-irradiation. It was speculated that this was indirectly due to a decrease in positive charge at the silicon-oxide interface. Modifications aimed at reducing radiation induced degradation are proposed for all three cell types.

Weinberg, I.↗
NASA NTRS1980

Radiation damage in high voltage silicon solar cells

High open circuit voltage cell designs based on 0.1 Ohm cm p-type silicon were irradiated with 1 MeV electrons and their performance determined to fluences as high as 10 to the 15th power per sq cm. Of the three cell designs, radiation induced degradation was greatest in the high low emitter (HLE) cell. The diffused and ion implanted cells degraded approximately equally but less than the HLE cell. Degradation was greatest in an HLE cell exposed to X-rays before electron irradiation. The cell regions controlling both short circuit current and open circuit voltage degradation were defined in all three cell types. An increase in front surface recombination velocity accompanied time dependent degradation of an HLE cell after X-irradiation. It was speculated that this was indirectly due to a decrease in positive charge at the silicon oxide interface. Modifications aimed at reducing radiation induced degradation are proposed for all three cell types.

Weinberg, I.↗
NASA NTRS1980

Refractory thermoelectric materials

The Seebeck coefficient and electrical resistivity of boron-carbon (B-C) and boron-carbon-silicon (B-C-Si)) P-type alloys are reported for temperatures up to 500 C. Using available literature values for the thermal conductivity of B-C alloys, thermoelectric figure-of-merit values of 1.37 x 10 to the -5th and 1.20 x 10 to the -4th/deg C are calculated for 100 and 500 C, respectively. Sulfur-deficient rare earth sesquisulfide N-type alloys exhibit Seebeck coefficients which are relatively insensitive to alloy composition over the composition range investigated but are very sensitive to fabrication parameters.

Elsner, N. B.↗
NASA NTRS1979

Semiconductor technology program. Progress briefs

The current status of NBS work on measurement technology for semiconductor materials, process control, and devices is reported. Results of both in-house and contract research are covered. Highlighted activities include modeling of diffusion processes, analysis of model spreading resistance data, and studies of resonance ionization spectroscopy, resistivity-dopant density relationships in p-type silicon, deep level measurements, photoresist sensitometry, random fault measurements, power MOSFET thermal characteristics, power transistor switching characteristics, and gross leak testing. New and selected on-going projects are described. Compilations of recent publications and publications in press are included.

Bullis, W. M.↗
DOE OSTI2024

Optical Modeling of Polysilicon: TOPCon PV

Determine how film thickness changes with different deposition methods. Analyze relationship between film thickness and optical constants. The deposition rate of intrinsic polysilicon is higher during initial deposition then begins to slow down as deposition time increases. Longer depositions of polysilicon are more crystalline in structure than shorter depositions. N-type doping of polysilicon is more crystalline in structure than p-type doping, despite similar film thicknesses.

Bruggeman effective media approximation↗
DOE OSTI2025

Hierarchical Hybrid Multifunctional Materials through Interface Engineering

This project focuses on the development of stimuli-responsive hybrid multifunctional materials. We place emphasis on the design, synthesis, structural characterization, evaluation of functional properties (electronic, thermal and optical) of several (1-x)Cu 2 Se/(x)WBGS hierarchical bulk composites between Cu 2 Se, a narrow band gap semiconductor (NBGS), with a range of wider band gap semiconductors (WBGS) such as CuMSe 2 (M = Al, Ga, In, Fe, Cr) and Cu 4 TiSe 4 . Cu2Se is a well-studied NBGS with excellent thermoelectric properties (high electrical conductivity, large thermopower, etc.) while CuMSe 2 and Cu 4 TiSe 4 are high performance solar absorber materials (large band gap, large absorption coefficient, etc.). Our primary objectives are (i) to demonstrate the ability to integrate dissimilar functional properties such as large optical absorption coefficient and high electronic conductivity, within (1-x)Cu 2 Se/(x)WBGS composite; and (ii) to establish the correlation between the hierarchical structural entanglement of Cu 2 Se with WBGS (CuMSe 2 or Cu 4 TiSe 4 ) phase, the interactions between native electronic defects within the coexisting phases in the resulting (1-x)Cu 2 Se/(x)WBGS bulk composites , and the impacts on their electronic conductivity, thermal transport and optical properties.

36 MATERIALS SCIENCE↗