The Past, Present and Future of Space Photovoltaics

This paper discusses the migration of crystalline space solar cell technology from silicon, to gallium arsenide then to the multiple junction devices in use today. Thin film technologies have migrated from the Cu₂S/CdS and similar cells to the amorphous silicon multijunction devices to copper indium diselenide devices. Array technologies have moved from flat plate arrays with shingled cells to concentrator arrays of several designs - some of which have reinvented 40-year old approaches. Crystalline cell efficiency in space has risen from about 10% to 30%, whereas thin film cell efficiency has risen from about 5% to 12%. Array specific power has gone from about 20 W/kg to over 300 W/kg (in design). Arrays have flown away from the sun to about 3 AU and are on their way to Mercury. Opportunities for future cell research will be included with the promise of devices with efficiencies over 40%