Efficiencies over ten percent have been achieved with three thin-film materials: amorphous silicon (a-Si), copper indium diselenide (CuInSe2), and cadmium telluride (CdTe). However, very little current research is aimed at depositing thin-film cells on lightweight substrates, since most of the applications being considered are terrestrial, where weight is not as critical. To enable their use in space, technology for deposition on extremely lightweight substrates will need to be developed. Thin film solar cells have not yet been demonstrated in space. A conservative projection of an achievable thin-film solar cell blanket usable for space would be a 5% efficient thin-film cell fabricated on a 25 micron thick Kapton substrate. This yields a photovoltaic blanket specific power of 1.7 kW/kg. An optimistic projection might be a 15% thin-film cell on a 7 micron thick Kapton substrate, leading to a photovoltaic blanket specific power of 15 kW/kg. These numbers compare favorably to current state of the art spacecraft solar blankets. Thin-film cells have other desirable features for space applications. In addition to low mass, thin-film photovoltaics are also projected to have considerably lower
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