We report on the synthesis of silicon and germanium nano-crystalline quantum dots (nc-QDs) for photovoltaic applications by means of ion implantation followed by annealing.Nucleation was achieved by implanting Si+ and/or Ge+ ions into SiO2 thin films, previously thermally grown on a Si(100) substrate, and annealing to 1100℃.The thickness of the oxide layer, the stoichiometry of the implanted layer, and the depth profiles of the implanted ions were determined for all samples by using both RBS and ellipsometry techniques.Characterization by TEM and SEM indicates that the diameter of the nc-QDs varies from 2 to 20 nm for Si and from 5 to 30 nm for Ge, which is in the range of the Bohr radius of bulk crystalline silicon (4.2 nm) or germanium (11 nm).We showed that germanium diffusion due to thermal annealing is reduced when the oxide layer is implanted with both silicon and germanium in the same range.Optical and electrical properties were investigated by PL and Ⅰ-V measurements.The electrical curves of the structures under illumination demonstrate the photovoltaic behavior of the nc-QDs.These results remain very promising and offer potentially unprecedented, vast improvements to third generation solar cells.