The construction of a Dye sensitized solar cell is fairly simple and can be easily explained. In general, a dye sensitized solar cell consists of the following parts which are listed in a sequence:
• Photo anode
• Semiconductor layer comprising of the dye
• Electrolyte layer
• Photocathode
Different materials have been experimented till date on these components of a dye sensitized solar cell and each material is found to produce a particular efficiency, within its own constraints. The popular materials which are used for the photo anode in the case of dye sensitized solar cell are ITO coated glass and FTO coated glass. These are also called as conductive glasses in general and conduct a fair amount of electricity generated without great loss.
The semiconductor layer popularly used is Titanium dioxide and nano titanium dioxide is mostly used. The particle size of this titanium dioxide is less than 100nm. This titanium dioxide layer is coated on the dye and the sensitized dye, also known as molecular sensitizer is absorbed on its surface. In the case of dye sensitized solar cell the popular dye used is a Ruthenium based Polypyridine dye. Ruthenium is generally preferred because of its longevity and prevents degradation of the dye sensitized solar cell.
Next is the electrolyte layer. The electrolyte layer is used for transferring the charges from the photo anode to the photo cathode and the efficiency of the dye sensitized solar cell mainly depends on the performance of the electrolyte. Different materials with the required properties are continuously experimented and the type of electrolyte depends upon the choice of the cell.
The photocathode is common in the case of most dye sensitized solar cells and the widely preferred one is made up of platinum metal.
Working of a dye sensitized solar cell:
The light rays which fall on the photo anode excite a photon when it strikes the dye coated on the surface of Titanium dioxide and this excited dye results in the injection of an electron in the semiconductor layer of titanium dioxide. The dye therefore loses one of its electrons and in order to get back its lost electron it takes one from the electrolyte and this process happens very quickly. The electrolyte which is one electron short diffuses and moves to the bottom of the cell where it gets back its lost electron from the photocathode as it has flown through the external circuit thereby constituting an electric current in the circuit. Thus a dye sensitized solar cell generates electricity.