GaAs thin-film solar cells

Thin-film solar cells utilizing polycrystalline gallium-arsenide films have been made and investigated to determine their suitability for future solar-power systems. The gallium-arsenide films are vapor deposited onto substrates of molybdenum or aluminum foil. Of the various junctions investigated, the most successful has been one consisting of a surface barrier employing an evaporated film of platinum or semiconducting copper selenide. The efficiencies of platinum gallium-arsenide barriers on molybdenum substrates have been 3 percent for 4 cm²area, 4.5 percent for 2 cm²area and 5 percent for 0.2 cm²area. For copper selenide gallium-arsenide barriers on molybdenum an efficiency of 4.6 percent for 0.73 cm²area has been measured; using aluminum substrates this figure is 4.3 percent for the same area with a power-to-weight ratio in excess of 135 watts per pound. With an etching treatment, cells made with copper selenide barriers have shown no degradation on the shelf or under load at room ambient.