Search NASA⌕ Search

SEARCH · Search NASA

Results for “Silicon Solar Cells”

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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Performance of high resistivity n+pp+ silicon solar cells under 1 MeV electron irradiation

High resistivity (1250 and 84 ohm-cm) n(+)pp(+) silicon solar cells were irradiated and their performance evaluated as a function of fluence. The greatest degradation in power occurred for the higher resistivity cell. The data were analyzed under open circuit conditions, and the components of V sub oc determined as a function of fluence. It was found that the voltage contributions from the front and back junctions decreased while the base component (V sub B) increased with fluence. The anomalous behavior of V sub B was attributed to an increase in the base minority carrier gradient with fluence. An argument that the increased power degradation in the 1250 ohm-cm cells was attributable to an increased voltage drop in the base is presented. Diffusion lengths calculated under high injection conditions were significantly greater than those determined under low injection. This was attributed to a saturation of recombination centers under high injection conditions.

Weinberg, I.↗
NASA NTRS1986

Toward a systematic design theory for silicon solar cells using optimization techniques

This work is a first detailed attempt to systematize the design of silicon solar cells. Design principles follow from three theorems. Although the results hold only under low injection conditions in base and emitter regions, they hold for arbitrary doping profiles and include the effects of drift fields, high/low junctions and heavy doping concentrations of donor or acceptor atoms. Several optimal designs are derived from the theorems, one of which involves a three-dimensional morphology in the emitter region. The theorems are derived from a nonlinear differential equation of the Riccati form, the dependent variable of which is a normalized recombination particle current.

Misiakos, K.↗
NASA NTRS1986

Use of low-energy hydrogen ion implants in high-efficiency crystalline-silicon solar cells

The use of low-energy hydrogen implants in the fabrication of high-efficiency crystalline silicon solar cells was investigated. Low-energy hydrogen implants result in hydrogen-caused effects in all three regions of a solar cell: emitter, space charge region, and base. In web, Czochralski (Cz), and floating zone (Fz) material, low-energy hydrogen implants reduced surface recombination velocity. In all three, the implants passivated the space charge region recombination centers. It was established that hydrogen implants can alter the diffusion properties of ion-implanted boron in silicon, but not ion-implated arsenic.

Fonash, S. J.↗
NASA NTRS1979

Silicon Materials Task of the Low Cost Solar Array Project, Phase 3. Effect of Impurities and Processing on Silicon Solar Cells

The effects of impurities, various thermochemical processes, and any impurity process interactions on the performance of terrestrial silicon solar cells are defined. Determinations of the segregation coefficients of tungsten, tantalum, and cobalt for the Czochralski pulling of silicon single crystals are reported. Sensitive neutron activation analysis was used to determine the metal impurity content of the silicon while atomic absorption was used to measure the metal content of the residual liquid from which the doped crystals were grown. Gettering of Ti doped silicon wafers improved cell performance by one to two percent for the highest temperatures and longest times. The HCl is more effective than POCl3 treatments for deactivating Ti but POCl3 and HCl produced essentially identical results for Mo or Fe.

Hopkins, R. H.↗
NASA NTRS1984

Towards a 20 percent efficient silicon solar cell

A project is underway at the University of New South Wales aimed at producing a 20 percent efficient silicon solar cell. A prerequisite for obtaining such a significant increase in cell efficiency is the improvement of the open circuit voltage of these cells. Two techniques are described which have produced experimental devices with open circuit voltages of 690 mV or higher. These high voltage techniques have been combined with other high efficiency design features to produce silicon cells with independently measured energy conversion efficiencies in excess of 19 percent under standard terrestrial test conditions (direct beam AM1.5 spectrum, 100 mW/sq cm, 28 C).

Green, M. A.↗
NASA NTRS1972

A reliable all-silver front contact for silicon solar cells

The feasibility of making an adherent and moisture degradation resistant silver-only front contact to silicon solar cells was demonstrated. Optimum fabrication processes and process sequences were determined for making such contacts. These contacts were found to also have good electrical characteristics. A back contact of aluminum-silver was also developed. This proved very satisfactory for low-temperature applications.

Lamneck, J. H., Jr.↗
NASA NTRS1974

Optimum design of antireflection coating for silicon solar cells

Based on classical electromagnetic theory, reflectivity calculations for various single and double optical coating systems for silicon solar cells are presented. From calculations and considerations of solar spectral response of the solar cells, the number and thickness of coating materials needed to obtain efficient solar cells can be predicted. Some experimental results on single layer coated cells are also presented for comparison with calculations, and agreement is good. By means of microwave transmission line analogy, the design of the multilayer coating can be simplified by using Tchebycheff polynomials.

Wang, E. Y.↗
NASA NTRS1975

Effects of high doping levels silicon solar cell performance

The significance of the heavy doping effects (HDE) on the open-circuit voltage of silicon solar cells is assessed. Voltage calculations based on diffusion theory are modified to include the first order features of the HDE. Comparisions of the open-circuit voltage measured for cells of various base resistivities are made with those calculated using the diffusion model with and without the HDE. Results indicate that the observed variation of voltage with base resistivity is predicted by these effects. A maximum efficiency of 19% (AM0) and a voltage of 0.7 volts are calculated for 0.1 omega-cm cells assuming an optimum diffused layer impurity profile.

Godlewski, M. P.↗
NASA NTRS1976

Optimized metallization patterns for large-area silicon solar cells

Design criteria is presented for optimizing the front-surface metallization pattern of large-area silicon solar cells. A computer program calculates the spacing of metal fingers which minimizes resistive and shadowing losses. Finger spacing and efficiency for the optimum design are presented as a function of finger width and cell size. It is shown that quantitative evaluation of metallization pattern options can be made without cell fabrication.

Matzen, W. T.↗
NASA NTRS1985

Theory of the high base resistivity n(+)pp(+) silicon solar cell and its application to radiation damage effects

Particulate radiation in space is a principal source of silicon solar cell degradation, and an investigation of cell radiation damage at higher base resistivities appears to have implication toward increasing solar cell and, therefore, useful satellite lifetimes in the space environment. However, contrary to expectations, it has been found that for cells with resistivities of 84 and 1250 ohm cm, the radiation resistance decreases as cell base resistivity increases. An analytical solar-cell computer model was developed with the objective to determine the reasons for this unexpected behavior. The present paper has the aim to describe the analytical model and its use in interpreting the behavior, under irradiation, of high-resistivity solar cells. Attention is given to boundary conditions at the space-charge region edges, cell currents, cell voltages, the generation of the theoretical I-V characteristic, experimental results, and computer calculations.

Goradia, C.↗
NASA NTRS1991

Reverse bias voltage testing of 8 cm x 8cm silicon solar cells

A study is described of the reverse I-V characteristics of the largest space qualified silicon solar cells currently available (8 x 8 cm) and of reverse bias voltage (RBV) testing performed on these cells. This study includes production grade cells, both with and without cover glass. These cells span the typical output range seen in production. Initial characteristics of these cells are measured at both 28 and 60 C. These measurements show weak correlation between cell output and reverse characteristics. Analysis is presented to determine the proper conditions for RBV stress to simulate shadowing effects on a particular array design. After performing the RBV stress the characteristics of the stressed cells are remeasured. The degradation in cell performance is highly variable which exacerbates cell mismatching over time. The effect of this degradation on array lifetime is also discussed. Generalization of these results to other array configurations is also presented.

Woike, T.↗
NASA NTRS1986

High-efficiency silicon solar cells - Development, current issues and future directions

This paper provides a review of material, process, and design considerations that are essential for achieving high-efficiency silicon solar cells. It describes an approach that resulted in 18.0-18.5-percent-efficient cells on low-resistivity float-zone silicon material. It is shown experimentally that a combination of surface passivation and double-layer antireflection coating can provide 2-3 percent (absolute) improvement in cell efficiency provided the material, process and cell design are carefully selected.

Rohatgi, A.↗
NASA NTRS1972

Results of a real-time irradiation of lithium P/N and conventional N/P silicon solar cells.

Eight types of lithium-diffused P/N and three types of conventional 10 ohm-cm N/P silicon solar cells were irradiated at four different temperatures with a strontium-90 radioisotope at a rate typical of that expected in earth orbit. The six-month irradiation confirmed earlier accelerator results, showed that certain cell types outperform others at the various temperatures, and, in general, verified the recent improvements and potential usefulness of lithium solar cells. The experimental approach and statistical methods and analyses employed yielded increased confidence in the validity of the results. Injection level effects were observed to be significant.

Reynard, D. L.↗
NASA NTRS1983

Relationship between the blue response and open-circuit voltage of high performance silicon solar cells

The relationship between the response at blue wavelengths and the open-circuit voltage of high performance silicon solar cells with a virtually 'transparent' emitter is analyzed. It is shown that a one-dimensional cell model cannot simultaneously model the optical collection properties and operating characteristics of such cells. The analysis highlights the importance of surface conditions and shows that previous conclusions regarding bounds on Auger coefficients imposed by correlating these parameters must be treated with caution.

Green, M. A.↗