Dye-sensitised solar cells using high mobility, transparent conducting oxides for tandem solar cell applications

Dye-sensitised solar cells are suitable for use as a top cell in a tandem solar cell structure, with a bottom CIGS solar cell, because their transmission characteristics can be adjusted by changing the particle size of the mesoporous TiO2 layer, and the photosensitising dye used. However, optical losses also occur from the fluorine doped tin oxide electrode, due to free carrier absorption in the NIR region of the solar spectrum, and lower the light available to the bottom cell. To solve this problem, a high mobility transparent conducting oxide (titanium doped indium oxide) has been used as the conducting layer to lower the optical loses in the near infrared through the cell. This increases light transmission from 800nm onwards, whilst maintaining high conductivity in the layer, which could be used in a tandem device. A device efficiency of 6.77% has been fabricated, whilst problems of porous layer delamination, and low temperature stability of the conducting layer have been solved.