Transport and interfacial transfer of electrons in dye-sensitized nanocrystalline solar cells

Current understanding of the mechanisms of electron transport and interfacial transfer in the dye-sensitized nanocrystalline solar cell is reviewed, and thermodynamic and kinetic aspects of the cell are related to cell performance. The current voltage characteristics of the I-3(-)/I- redox couple on platinum and on bare as well as TiO2-coated tin oxide glass substrates has been studied using thin layer cells, and the capacitance voltage characteristics of the fluorine doped tin oxide substrate (bare and TiO2 coated) have been determined by electrochemical impedance spectroscopy. A charge extraction method is described, which provides a new way to obtain information about the distribution of electron trapping states and the kinetics of the back reaction of electrons with tri-iodide ions in the electrolyte. The analysis of the data and sources of error is discussed, and the results are compared with the intensity dependent behavior revealed by small amplitude perturbation methods. The discussion highlights the importance of the competition between electron transport and back reaction in determining cell performance. (C) 2002 Elsevier Science B.V, All rights reserved.