Effects of surface treatments on high mobility ITiO coated glass substrates for dye sensitized solar cells and their tandem solar cell applications

Dye sensitized solar cells (DSCs) have the potential to be used as a top device in a tandem solar cell structure with a bottom Cu(In,Ga)Se2 (CIGS) cell. Optical losses, however, within the fluorine doped tin oxide (FTO) conducting electrode used with DSCs limit the light available for the bottom cell for photocurrent generation, and therefore the whole device. High mobility transparent conducting oxides have the potential to reduce these optical losses, since the transmission in the near infrared of these substrates is high compared to standard conducting oxides. Attempts have in the past been made to use these conducting oxide substrates as the electrodes in DSCs; however delamination of the deposited TiO2 layer and an increase in sheet resistance of the high mobility material have caused problems. Here we present alternative surface treatments to ensure that delamination is significantly reduced, as well as a method to recover lost conductivity of heated indium oxide films, which result in transparent cells of over 7% efficiency, which is close to that reached on standard FTO substrates.