Transparent conductive oxideless tandem dye-sensitized solar cells consisting of light-splitting structures

Fiber and pillar tandem dye-sensitized solar cells (DSCs), which do not need transparent conductive oxideless layer tandem cells (TCO-less TAN), are fabricated and their fundamental tandem properties are evaluated. TCO-less TAN cells consist of a light-splitting waveguide and TCO-less DSCs. The TCO-less DSC is composed of a nanoporous titania back-contacted with a porous Ti electrode or a nanoporous titania sheet supported by a stainless steel mesh whose surface was protected with TiOx thin layers. Two kinds of light-splitting structures are introduced. One is a light-splitting structure in which polystyrene particles with different diameters are dispersed in water. The other consists of dichroic mirrors. These light-splitting structures are coupled with TCO-less DSCs stained with dyes absorbing light corresponding to these split lights. Open circuit voltages (Voc) of these TCO-less tandem DSCs are two times (two tandem structure) or three times (three tandem structure) higher than those of the corresponding single cells, demonstrating that these structures work as tandem cells.