Engineering topics

Osterwald, C. R.

Publications and source records attributed to Osterwald, C. R..

4 records

NASA NTRS1991

Monolithic InP/Ga0.47In0.53As tandem solar cells for space

A review is provided of progress made in the development of InP/Ga(0.47)In(0.53)As monolithic tandem solar cells since the last SPRAT conference. Improved one-sun, three terminal tandem designs have resulted in Air Mass Zero (AM0) efficiencies as high as 23.9 pct. at 25 C. Additionally, high efficiency concentrator versions of the three terminal device were developed. The best concentrator tandem has a peak AM0 efficiency of 28.8 pct. under 40.3 suns at 25 C. For the concentrator tandems, the subcell performance parameter temperature coefficients are reported as a function of the concentration ratio. Results from a computer modeling study are presented which provide a clear direction for improving the efficiency of the concentrator tandem. The prospects for fabricating high efficiency, series connected (i.e., two terminal) InP/Ga(0.47)In(0.53)As monolithic tandem cells are also discussed.

Wanlass, M. W.↗

NASA NTRS1991

Modeled performance of monolithic, 3-terminal InP/Ga(0.47)In(0.53)As concentrator solar cells as a function of temperature and concentration ratio

Using measured device parameters from a monolithic three-terminal In/GaInAs (0.75 eV) tandem concentrator solar cell, a numerical model is constructed that calculates efficiency as a function of temperature and concentration ratio. The device measurements indicate that the series resistance in the InP top cell severely limits the maximum efficiency at high concentration ratios. Results from the model in which a single-junction InP concentrator solar cell that has a lower resistance by a factor of six was substituted for the top cell show that peak 20 C air-mass-zero (AM0) efficiencies should approach 30 percent at concentration ratios greater than 100. At 80 C, this tandem cell should exceed 24 percent AM0 efficiency.

Osterwald, C. R.↗

NASA NTRS1991

InP concentrator solar cells

The design, fabrication, and characterization of high-performance, n(+)/p InP shallow-homojunction (SHJ) concentrator solar cells are described. The InP device structures were grown by atmospheric-pressure metalorganic vapor phase epitaxy. A preliminary assessment of the effects of grid-collection distance and emitter-sheet resistance on cell performance is presented. At concentration ratios of around 100, cells with efficiencies of 21.4 percent AM0 (24.3 percent direct) at 25 C are fabricated. These are the highest efficiencies yet reported for single-junction InP solar cells. The performance of these cells as a function of temperature is discussed, and areas for future improvement are outlined. Application of these results to other InP-based photovoltaic devices is discussed.

Ward, J. S.↗

NASA NTRS1990

Primary reference cell calibrations at SERI - History and methods

The tabular calibration method used at the Solar Energy Research Institute (SERI) for primary reference cells is derived and described in detail. An uncertainty analysis shows that the tabular method should have a total uncertainty of + or - 1.0 percent; data from five years of calibrations are then shown to support this analysis. Results from SERI's tabular method are compared with terrestrial calibrations performed by the NASA Lewis Research Center in the late 1970s.

Osterwald, C. R.↗