We propose a new type of dye-sensitized solar cell (DSC) using carbon nanotubes (CNTs). Recently, global warming
due to CO<sub>2</sub> generated from power plants, cars, and so on has received much attention. Therefore, clean power, e.g., solar power, is gaining in importance. In this study, we focused on a DSC that uses CNTs. Generally, sensitized dyes on
semiconducting and metallic electrodes are used for constructing DSCs. In contrast, CNTs have many excellent
properties. In particular, they have metallic and semiconducting properties that are used for the electrodes of DSCs.
Therefore, we applied CNTs for fabricating a new “painting-type” DSC with semiconducting and metallic electrodes.
CNTs are dispersed in water with surfactant to prepare CNT-paste for painting. This resulting CNT-paste has the same
properties as a normal CNT. A DSC is comprised of two electrodes. One is a semiconducting electrode with a sensitized
dye and another is a metallic one, as mentioned above. We fabricated the two electrodes by painting the CNT-paste onto
substrates. Thus, this type of DSC can be applied to various objects, for example, the wall and car and housetop. An
electrolyte is required and must be put between the electrodes. The method for fabricating a painting type DSC is very
simple. First, two versions of the paste are used. One is a semiconducting CNT-paste that adsorbs a dye and the other is a
CNT-paste without a dye. Second, we paint each paste onto two substrates. Finally, the two substrates are stacked. We
drip about 10μl of an electrolyte onto the stacked substrates and irradiate them with solar light (1300 W/m<sup>2</sup>). An
electromotive force (EMF) is generated by excited electrons from the dye, which are adsorbed on the semiconducting
electrode. The maximum EMF reached about 250 mV and the current reached about 10 μA. These results indicate that
the proposed painting-type DSC can be used a new type of solar cell.