Si quantum dot-sensitized solar cells using Si nanoparticles produced by plasma CVD

We have fabricated Si quantum dot-sensitized solar cells by three assembling methods; the conventional method and two novel methods in which Si nanoparticles/TiO ₂ blend paste is coated onto FTO glass, or TiO ₂ film. The highest current density is realized s solar cell for which Si nanoparticles/TiO ₂ blend paste is coated onto TiO ₂ films. The result indicates that excitons generated in Si nanoparticles are separated into electrons and holes and such carriers are extracted to the outer circuit. Photon-to-current conversion efficiency (PCE) of our Si quantum dot-sensitized solar cells is larger than that of the cell without Si nanoparticles in a wavelength range below 500nm. It suggests that carrier generation in the Si nanoparticles is realized in the wavelength range less than 500 nm in the solar cell. Light intensity dependence of photo-current density shows superliner one for photon energy larger than twice of the bandgap energy of the Si nanoparticles.