A breakthrough that could dramatically reduce the weight of high-power solar cells for satellites and high-altitude airships is being claimed by a US manufacturer of semiconductor-based components.

Albuquerque, New Mexico-based Emcore says its inverted metamorphic (IMM) all-silicon cells, developed under a US Air Force Research Laboratory (AFRL) contract, are 31% efficient in turning light into electricity despite being a fraction of the weight of conventional cells.

Typically a multi-junction photovoltaic cell has three layers, one of germanium and two of silicon, which are used to capture light in different frequencies. Multi-junction cells produced by Emcore for terrestrial applications have reached 37% peak conversion efficiency, but the IMM cell is just 1/15th the thickness of these.

The weight reduction is achieved by growing the cells "upside down", enabling removal of the germanium used for the bottom layer of the existing cells and leaving just the two silicon layers.

"Achievement of 31% conversion efficiency will enable new space power applications," says Emcore president and chief operating officer Hong Hou. The company expects the new cells to be released commercially around 2010.

The AFRL is interested in lightweight, powerful solar cells for satellites and high-altitude airships that can act as long-endurance communication relays and surveillance platforms.

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Source: FlightGlobal.com