Three-Dimentional (3D) Solar Cell Why is CuInS2 considered a promising candidate? 1. High absorption coefficient. 2. Direct band gap of 1.55 eV, which is well matched to the solar spectrum. The advantage of using nanostructured materials is that light absorption and charge migration occur no longer in one material (usually silicon)

1. Glass coated with a fluor-doped SnO2 is used as substrate. 2. TiO2 is deposited on the substrate by spray deposition to prevent the contact between CuInS2 and SnO2 which leads to leakage current. 3. Next, a nanocrystalline anatase TiO2 coating is applied to form the electron-conducting matrix. 4. To complete the devices, an electrical contact is applied on top, which can be obtained by doctor blading of graphite paste. 5. A previous study has shown that the electronic contact between TiO2 and CuInS2 is improved significantly if a barrier film of Inx (OH) yS2 is deposited prior to CuInS2 deposition. The function of this barrier film is to align the valence bands and to suppress the back flow of electrons.

a&b : TCO layer Transparent Conducting Oxide (F:SnO2) c: dense TiO2 d: nanocomposite TiO2/In2S3/CuInS2 e:near to the surface