The important features that distinguish DSC from conventional photovoltaics are as follows:
- It is a photoelectrochemical cell: charge separation occurs on interface between a wide bandgap semiconductor and an electrolyte.
- It is a nanoparticulate titania cell: it is not a dense film as is amorphous silicon, but a "light sponge".
- It is a Dye-sensitised cell: a dye monolayer chemically absorbed on the semiconductor is a primary absorber of sunlight; free charge carriers are generated by electron injections from a dye molecule, excited by visible radiation.
The basic titania (TiO2) based DSC cell consists of a sandwich of TiO2, dye, electrolyte and catalyst between two conductive transparent electrodes. Upon illumination of the cell, charge separation occurs by electron injection from the excited state dye molecule into the conduction band of TiO2. Simply, light excites the dye, sending an electron on its way to be picked up and transmitted by the semiconducting titania to become electrical energy. The dye is then reduced by an electron transferred by the redox couple.
