Solar-cell efficiency nearly doubled by Hughes' spectrolab

Citation

(1998), "Solar-cell efficiency nearly doubled by Hughes' spectrolab", Aircraft Engineering and Aerospace Technology, Vol. 70 No. 1. https://doi.org/10.1108/aeat.1998.12770aab.007

Solar-cell efficiency nearly doubled by Hughes' spectrolab

Solar-cell efficiency nearly doubled by Hughes' spectrolab

Spectrolab Incorporated, a unit of Hughes Electronics Corporation, has announced the successful operation of a revolutionary dual-junction, gallium-arsenide solar cell which will nearly double the efficiency of traditional silicon cells used on spacecraft solar-array panels.

Spectrolab's gallium-arsenide, dual-junction solar cells are the result of more than ten years of development, but with the launch of PanAmSat Corp.'s PAS-5 satellite last year, the cells made their first voyage into space and are the first in use on a commercial communications satellite.

"Because the power is nearly doubled, these dual-junction cells enable us to provide solar panels which are either twice the power or half the weight," said Dieter Zemmrich, president of Spectrolab. "This advanced technology enables our customers to be more flexible in their satellite design, a benefit which has great competitive advantage."

A solar cell is basically a semiconductor with the ability to convert the light from the sun into electrical energy. The dual-junction, gallium-arsenide solar cells can convert 21.6 percent of the sun's energy into power, as compared with the traditional silicon solar cells, which can convert only 12.3 percent.

Dual-junction solar cells measure approximately 27 cm² (4.2 square inches) in area and 0.140 mm (0.0055 inches) in thickness. The cells are "grown", atom by atom, in an epitaxial growth chamber using 100-millimeter diameter, single-crystal germanium wafers as a supporting substrate. The germanium wafer provides the crystalline structure upon which to "grow" the single-crystal, solar-cell layer.

Two solar cells are layered on top of each other, and because each converts a different part of the light spectrum, the solar cell can more efficiently convert sunlight into electrical power. As the sun's rays hit the top layer of gallium-indium phosphide, short wavelengths are converted into electrical power.

Because gallium-indium phosphide is transparent to long wavelengths, these actually pass through to the gallium-arsenide layer, where they too are converted into electrical power, thus creating the second, or dual, junction. This simultaneous function is unique to the dual-junction solar cells and is the basis for the increased efficiency.

The PAS-5 satellite, built by Hughes Space and Communications Co., uses nearly 15,000 dual-junction, gallium-arsenide solar cells to convert the sun's rays into 10 kilowatts of power at beginning of life, a substantial increase over the 4.8 kilowatts provided by a standard HS 601 satellite. PAS-5's 10 kilowatts will provide the power necessary to broadcast direct-to-home and other television services in Latin America for 15 years.

Details from Hughes Europe S.A., Avenue Ariane 5, B-1200 Brussels, Belgium. Tel: 322 778 49 11; Fax: 322 778 49 99.