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Brandhorst, H. W., Jr.

Publications and source records attributed to Brandhorst, H. W., Jr..

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Surface photovoltage method extended to silicon solar cell junction

The conventional surface photovoltage (SPV) method is extended to the measurement of the minority carrier diffusion length in diffused semiconductor junctions of the type used in a silicon solar cell. The minority carrier diffusion values obtained by the SPV method agree well with those obtained by the X-ray method. Agreement within experimental error is also obtained between the minority carrier diffusion lengths in solar cell diffusion junctions and in the same materials with n-regions removed by etching, when the SPV method was used in the measurements.

Wang, E. Y.↗
NASA NTRS1974

Rapidly pulsed, high intensity, incoherent light source

A rapid pulsing, high intensity, incoherent light is produced by selectively energizing a plurality of discharge lamps with a triggering circuit. Each lamp is connected to a capacitor, and a power supply is electrically connected to all but one of the capacitors. This last named capacitor is electrically connected to a discharge lamp which is connected to the triggering circuit.

Evans, J. C., Jr.↗
NASA NTRS1974

Low-high junction theory applied to solar cells

Recent use of alloying techniques for rear contact formation has yielded a new kind of silicon solar cell, the back surface field (BSF) cell, with abnormally high open-circuit voltage and improved radiation resistance. Several analytical models for open-circuit voltage based on the reverse saturation current are formulated to explain these observations. The zero surface recombination velocity (SRV) case of the conventional cell model, the drift field model, and the low-high junction (LHJ) model can predict the experimental trends. The LHJ model applies the theory of the low-high junction and is considered to reflect a more realistic view of cell fabrication. This model can predict the experimental trends observed for BSF cells.

Godlewski, M. P.↗
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 NTRS1974

The multiple junction edge illuminated solar cell

The multiple junction edge illuminated solar cell (M-J Cell) was devised for high voltage, low current applications. Devices to be flight-tested in early 1974 with 96 series-connected PNN+ junctions in a 2 cm x 2.3 cm size deliver 36 volts at 1 milliampere. Test data of M-J Cells fabricated with resistivities of 10, 50, 100, 200, 450, and 1000 ohm-cm silicon are presented and problem areas are discussed. An additional potential application of the M-J Cell lies in utilization of its high-intensity performance that has been demonstrated at levels in excess of 100 AMO suns.

Sater, B. L.↗
NASA NTRS1974

Performance of epitaxial back surface field cells

Epitaxial back surface field structures were formed by depositing a 10 micron thick 10 ohm-cm epitaxial silicon layer onto substrates with resistivities of 0.01, 0.1, 1.0 and 10 ohm-cm. A correlation between cell open-circuit voltage and substrate resistivity was observed and was compared to theory. The cells were also irradiated with 1-MeV electrons to a fluence of 5 times 10 to the 15th electrons per sq cm. The decrease of cell open-circuit voltage was in excellent agreement with theoretical predictions and the measured short-circuit currents were within 2% of the prediction. Calculations are presented for optimum cell performance as functions of epitaxial layer thickness, radiation fluence, and substrate diffusion length.

Brandhorst, H. W., Jr.↗
NASA NTRS1974

The drift field model applied to the lithium-containing silicon solar cell

The drift field model used by Wolf (1963) to calculate the short-circuit current was extended to permit calculations of the open-circuit voltage and the maximum power under conditions of illumination of either tungsten (2800 C) source or air mass zero sunlight. Voltages were calculated using an expression for the drift field diode saturation current. The model, applied to the oxygen-rich (C-13 group) lithium solar cells, was used to calculate the pre- and post-electron bombardment trends of the open-circuit voltage, maximum power, and short-circuit current for lithium gradients in the range from 10 to the 18th power to 10 to the 19th power Li/cm to the 4th power. Diffusion length degradation and carrier removal effects were sufficient to predict the cell performance up to 3 x 10 to the 14th electrons per sq cm. Beyond this fluence it was necessary to include drift field removal effects.

Godlewski, M. P.↗
NASA NTRS1973

The multiple junction edge illuminated solar cell

The multiple junction edge illuminated solar cell was devised for high voltage low current applications. Devices to be flight tested in early 1974 with 96 series connected PNN+ junctions in a 2 cm X 2.3 cm size deliver 36 volts at 1 milliampere. Test data of M-J cells fabricated with resistivities of 10, 50, 100, 200, 450, and 1000 ohm cm silicon are presented and problem areas are discussed. An additional potential application of the M-J cell lies in ultilization of its high intensity performance that has been demonstrated at levels in excess of 100 AMO suns.

Sater, B. I.↗
NASA NTRS1973

Performance of epitaxial back surface field cells

Epitaxial back surface field structures were formed by depositing a 10 micron thick 10 Omega-cm epitaxial silicon layer onto substrates with resistivities of 0.01, 0.1, 1.0 and 10 Omega-cm. A correlation between cell open-circuit voltage and substrate resistivity was observed and was compared to theory. The cells were also irradiated with 1 MeV electrons to a fluence of 5 X 10 to the 15th power e/cm2. The decrease of cell open-circuit voltage was in excellent agreement with theoretical predictions and the measured short circuit currents were within 2% of the prediction. Calculations are presented of optimum cell performance as functions of epitaxial layer thickness, radiation fluence and substrate diffusion length.

Brandhorst, H. W., Jr.↗
NASA NTRS1973

The drift field model applied to the lithium-containing silicon solar cell

The drift field model used by Wolf to calculate the short-circuit current was extended to permit calculations of the open-circuit voltage and the maximum power under conditions of illumination of either tungsten (2800 C) source or AMO sunlight. Voltages were calculated using an expression for the drift field diode saturation current derived here. The model, applied to the oxygen rich (C-13 group) lithium solar cells, was used to calculate the pre-and post-electron bombardment trends for lithium gradients in the range of 10 to the 18th power to 10 to the 19th power Li/cm to the 4th power. Published experimental data characterizing these cells were used to tailor the model. The calculated trends are in reasonable agreement with the empirical data of Faith. Diffusion length degradation and carrier removal effects were sufficient to predict the cell performance up to 3 x 10 to the 14th power e/sq cm. Beyond this fluence it was necessary to include drift field removal effects.

Godlewski, M. P.↗
NASA NTRS1973

Low-high junction theory applied to solar cells

Recent use of alloying techniques for rear contact formation has yielded a new kind of silicon solar cell, the back surface field (BSF) cell, with abnormally high open circuit voltage and improved radiation resistance. Several analytical models for open circuit voltage based on the reverse saturation current are formulated to explain these observations. The zero SRV case of the conventional cell model, the drift field model, and the low-high junction (LHJ) model can predict the experimental trends. The LHJ model applies the theory of the low-high junction and is considered to reflect a more realistic view of cell fabrication. This model can predict the experimental trends observed for BSF cells. Detailed descriptions and derivations for the models are included. The correspondences between them are discussed. This modeling suggests that the meaning of minority carrier diffusion length measured in BSF cells be reexamined.

Godlewski, M. P.↗
NASA NTRS1972

Silicon solar cell efficiency - Practice and promise.

The maximum efficiency of silicon solar cells is calculated and yields a value near 18%. Additionally, the performance of these high efficiency cells in a synchronous orbit radiation field is calculated and indicates that these cells would be superior to present silicon cells at all times. The performance of conventional cells is analyzed and several areas in which performance gains may be achieved are discussed. These areas include improvements in diffused region profile, in reduction of excess forward currents in cells made from low resistivity material and in the theory for describing complex solar cell structures.

Brandhorst, H. W., Jr.↗
NASA NTRS1972

Silicon solar cell efficiency: Practice and promise

The maximum efficiency of silicon solar cells was calculated and yielded a value near 18%. Additionally, the performance of these high efficiency cells in a synchronous orbit radiation field was calculated and it is suggested that these cells would be superior to present silicon cells. The performance of conventional cells was analyzed and several areas in which performance gains may be achieved are discussed. These areas include improvements in diffused region profile, in reduction of excess forward currents in cells made from low resistivity material, and in the theory for describing complex solar cell structures.

Brandhorst, H. W., Jr.↗
NASA NTRS1971

Calibration of solar cells using high-altitude aircraft.

A high altitude airplane has been used to obtain the outer space short circuit current of solar cells. The solar cells are mounted in a collimating tube and are measured at approximately 5000 foot intervals between 12,000 and 47,000 feet. The air mass is calculated for each altitude using the standard formula and the resulting curve is extrapolated to air mass zero. The effects on the solar cell output of a haze layer located at the tropopause has been observed. It is necessary to fly above this layer to ensure accurate results. Airplane calibrations of several primary standard cells calibrated on high altitude balloons show agreement within 0.5 per cent. Prediction of the output of satellite power supplies using airplane calibrated cells shows an accuracy of better than 1 per cent.

Brandhorst, H. W., Jr.↗