Dye-sensitized solar cells
Dye-sensitized solar cells (DSCs) convert solar radiation into electricity efficiently and cost-effectively by means of a light-harvesting sensitizer anchored to a high surface area nanoporous semiconductor film. The dye-sensitized solar cells belongs to the class of 3rd generation solar cells and currently is at the transition from applied R&D to industrial production.
At the ICP we are engaged in modeling and simulation of dye-sensitized solar cells. Our DSC models describe the physical and electrochemical processes within the device by means of partial differential equations. Solving these equations using in-house software tools, we can simulate the performance of the DSC under operating conditions and make model-based predictions for different cell configurations. The losses in the energy conversion can be assessed quantitatively.
In several applied R&D projects with academic and industrial partners we use these simulations in order to better understand the behavior of the devices, to enhance their lifetime and to enahnce their efficiency. For reaching these goals a close interplay between modeling, simulation,and validation from measurement data is the key stone.
The dye-sensitized solar cell converts electromagnetic radiation (e.g. sun light) into electrical energy. In DSCs the photons of the electromagnetic radiation are absorbed by a dye molecule in contrast to conventional silicon solar cells. The dye-molecules are adsorbed on the surface of a nanoporous semiconductor material (normally titanium dioxide). By the aborption an electron of the dye molecule is lifted to an excited energy state . This excited electron is then transferred to theconduction band level of the semiconductor and the dye molecule is oxidized. The dye is in contact with a redox electrolyte, which returns the missing electron to the dye molecule.
The most common electrolytes contain triiodide and iodide as the redox couple. In this case the dye is reduced by iodide and triiodide is formed. The injected electrons in the semiconductor are transported to the front contact mainly due to diffusive processes. The electrons from the front contact flow through the external load. At the back contact the electrons reduce triiodide to form iodide. Iodide is transported to the dye molecules at the semiconductor material and triiodide is transported from there to the back contact, which closes the electric circuit.