An interesting and innovative approach to the industrial fabrication of nc – DSCs is to use a single-faced monolithic structure of consecutive porous layers. In terms of production costs, the advantage of this concept over the ‘standard’ glass/glass design is that only one TCO-glass plate is required for a series connection of integrated cells, as is also known from amorphous silicon technology. This construction principle was first suggested in the literature by Kay and Gratzel . An AM 1.5 efficiency of 5.3% has been reported for a small module (20 cm2) containing 6 series-connected monolithic cells of
x 0.7 cm2.
Figure 7.5 illustrates the nc-DSC construction principle in the monolithic setup. Firstly, a layer of nanocrystalline ТЮ2 is applied as the photoelectrode. On top of this, a porous insulating oxide layer (Zr02) acts as a spacer. Finally, a porous graphite layer activated by carbon black pigments serves as counter electrode for’ the iodide/iodine-containing electrolyte. All three layers of the cell can be deposited by screen or stencil printing techniques on prestructured TCO-glass. At this stage, the layers are sintered, after which dye and electrolyte are applied, and finally a non-functional material, which only serves to seal and insulate the cell, covers the whole module.