Electronic Design

Large-Area Dual-Junction Solar Cells Achieve Record 25.3% Efficiency

Employing its metal-oxide chemical-vapor-deposition (MOCVD) process, EMCORE Corp., Somerset, N.J., has manufactured and shipped what it says is the world's highest-efficiency dual-junction solar cell for satellite applications. Based on customary satellite industry metrics, an efficiency of 25.3% was achieved for large-area (27.5-cm2) solar cells.

This is an important parameter since solar cells are one of the most significant economic drivers in satellite communications. Such a high efficiency translates to enhanced performance that increases revenue generation for satellite owners. Additionally, as satellites become more economical, they become a viable alternative for transmitting voice and Internet traffic.

"This represents a remarkable achievement by our staff at the EMCORE PhotoVoltaics Division in Albuquerque, N.M., which has been in operation for only 14 months,'' explains Reuben Richards, president and CEO of EMCORE. "Our cells reach far beyond the capability of silicon-based solar cells, which have a theoretical maximum efficiency of approximately 19% and degrade quite rapidly during orbit. The use of EMCORE's compound semiconductor cells equates to fewer devices being needed, resulting in smaller, lighter satellites with longer lifetimes, while providing more power. This initial efficiency record has been achieved through critical technology breakthroughs in tandem with state-of-the-art automated processing."

To get these results, the company uses indium-gallium-phosphide/gallium-arsenide (InGaP/GaAs) compound semiconductor solar cells. These cells are grown on a germanium substrate and have a minimum average efficiency of 23% at air mass zero (AMO) at 28°C. EMCORE is currently manufacturing the new dual-junction cells on a seven-day, 24-hour production schedule to accommodate current and projected contract demands.

EMCORE also has produced high-efficiency triple-junction cells with a minimum average of 26% AMO in pilot runs at the Albuquerque facility. These cells have completed preliminary radiation testing at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. JPL has verified an enhanced radiation stability with a power degradation of only 8% for an equivalent life of 15 years in geostationary orbit.

EMCORE's advanced solar cells are produced on the company's TurboDisc MOCVD tools, which feature stringent quality controls. EMCORE also achieved ISO 9001 certification last November.

Further details about the company and its products are accessible at www.emcore.com/solarcell/index.html. Contact Tom Miehe, vice president of marketing and sales, at (732) 271-9090, ext. 4188, or [email protected]

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