Future space missions will require Solar cell arrays having specific power ratings in excess of 1000 W/kg. Conventional crystalline photovoltaic technology comprised of epitaxial photovoltaic semiconductor materials grown on single crystal semiconductor substrates, cannot provide these specific ratings. We propose to synthesize nano-precursors of solar cell materials of uniform size by Solvo-thermal process. These nano-precursors will be deposited as nano-thin film on low cot and flexible metal foil substrate by Electrophoretic technique. Through subsequent , insitu annealing, thin films with grain size >50 microns will be produced. GaAs, Ge and InP will be investigated to determine which material can be deposited as high quality large grain thin film without contamination. The synthesized nano-precursors, electrphoretically deposited nano-thin film and large grain thin film produced after annealing will be fully characterized. A combination of crystalline thin film photovoltaic layers having an efficiency of just 25% fabricated on low cost, light weight flexible substrate such as a metal foil, would yield a specific power rating of >1200 W/kg. During Phase II multi-junction solar cell will be grown on the large grain thin film produced during Phase I on flexible/low cost metal foil substrate.