An approach for low-cost, thin-film polycrystalline GaAs solar cells on large-area silicon-based substrates is described. A proprietary Silicon-Film™ sheet material serves as an inexpensive substrate on which large-grain (>2 mm) polycrystalline GaAs films can be grown. The GaAs films are grown by a simple close-spaced vapor transport (CSVT) technique. A recrystallized Ge1−xSix buffer layer between the GaAs epilayer and Silicon-Film substrate can facilitate growth of the GaAs. A selective mode of growth to reduce thermal stress and lattice mismatch effects, along with a new interconnection scheme using a transparent conducting oxide, is described.An approach for low-cost, thin-film polycrystalline GaAs solar cells on large-area silicon-based substrates is described. A proprietary Silicon-Film™ sheet material serves as an inexpensive substrate on which large-grain (>2 mm) polycrystalline GaAs films can be grown. The GaAs films are grown by a simple close-spaced vapor transport (CSVT) technique. A recrystallized Ge1−xSix buffer layer between the GaAs epilayer and Silicon-Film substrate can facilitate growth of the GaAs. A selective mode of growth to reduce thermal stress and lattice mismatch effects, along with a new interconnection scheme using a transparent conducting oxide, is described.