Materials Selection

The transparent coating for the negative terminal is made of a thin layer of fluorine-doped tin oxide. It is a substrate that allows sunlight to pass through, meanwhile conducts electricity.
As for the semiconductor, either zinc oxide (ZnO) or titanium dioxide (TiO2) can be used. TiO2 is used and preferred because its surface is highly resistant to continued electron transfer. But it is not sensitive to visible light; it only absorbs small amount of solar photons, therefore, dye sensitizers are needed to attach to the titanium dioxide layer to harvest large portion of the sun light. ZnO has a higher electron mobility compared to TiO2, but has a limited selection of organic dyes, which makes it less desirable until better alternative sensitizers are discovered. Dye-sensitizers can be made of different types of materials. One option is the natural dye, which come from various resources such as blue berries, blackberries, and raspberries. They are easy to come by and good for school training courses or testing purposes. Another option is the synthetic dye, which gives better performance due to its optimized light collection property. The material for the positive terminal layer or the cathode layer can be from either platinum or carbon (graphite). The platinum has a higher efficiency; however, the carbon alternative is easier and less expensive, good for school works or testing purposes.