Characterization of a dye-sensitised titania solar cell electrode

Full text: Recently, dye-sensitised photoelectrochemical solar cells have become an alternative to present day p-n junction photovoltaic devices. Due to the simple constructions of these solar cells the production cost is lower than conventional PV cells. In order to improve the currently produced solar cell conversion efficiency, appropriate characterizations of every component in the cell and their effect when the cell is operating should be performed. We have characterised a dye-sensitised nanocrystalline titania film using variety of techniques. The aim of these experiments was, to investigate the micro structure of the films; to determine the penetration and amount of the dye in the film; and to clearly understand the properties of each element in the film. From Transmission Electron Microscopy the particles were seen as mixtures of tetrahedral and rhombohedral geometries with size distribution in the rage between 10 and 25 nm. These particles were identified by X-ray Diffraction as nano-crystals of anatase and brookite phases. The film was sensitised with a ruthenium (II) based dye for different times (between 0.5 and 24 hours) and the penetration and coverage of the dye was studied using Secondary Ion Mass Spectroscopy as well as Confocal Laser Scanning Microscopy. The dye was found to percolate uniformly through the whole of the titania film irrespective of the dyeing time. The penetration of the dye molecules up to the film-substrate interface is important for an efficient flow of the injected electrons to the conducting substrate. Using Rutherford Back Scattering, the composition of the film was determined and found to be 1 wt% Ru on maximum sensitisation. The optical properties of the dye-sensitised films were also measured which resulted in an increase of absorbance and a decrease of transmittance for dyeing times up to 8 hours. Beyond this time the values remained unchanged and thus a semi-transparent film with luminous transmittance between 0.30 and 0.65 were obtained