Thin film poly III–V space solar cells

Results on the development of polycrystalline III–V based devices grown by OMVPE on thin metallic foil substrates are presented. It has previously been demonstrated that device quality polycrystalline Ge suitable for OMVPE growth can be produced on metallic foils using a recrystallization process. This work reports on the development of textured metal foil substrates with low misfit grain boundary orientations designed to improve the semiconducting device parameters of the “epitaxially” deposited Ge films, the use of innovative device structures, and grain boundary passivation approaches for the polycrystalline GaAs films that are all designed to address performance issues associated with these types of solar cells. The Ge which serves as the III-V growth template could be activated and serve as the bottom junction of a conventional triple junction III-V cell design using this approach. The crystallographic, morphological, and electro-optical properties associated with these substrates and related epitaxial films will be presented. In addition, the thermal and radiation behavior, that is critical for the potential use of these devices in space, was investigated. The potential for these devices for future space development and exploration will be discussed.