Friedrich, D.; Kunst, M.: Analysis of charge carrier kinetics in nanoporous systems by time resolved photoconductance measurements. The Journal of Physical Chemistry C 115 (2011), p. 16657-16663
10.1021/jp200742z
Abstract:
A quasi-solid-state dye-sensitized solar cell is presented, where an electrolyte film replaces the conventional liquid electrolyte, reaching a solar light-to-current conversion efficiency of 3%. This proves the importance of surface conduction of the positive charge, e.g., via the Grotthuss mechanism. Contactless transient photoconductance measurements were performed on operating cells, revealing decay behavior of photoinduced charge carriers, dependent on external applied potential conditions. The measurements show that the decay is controlled by the injection of electrons into the front contact, hindered or enhanced by the field in the space charge region. Furthermore, the influence of redox molecules on the decay of photogenerated charge carriers in sensitized TiO2 films was analyzed and found to be dependent on the redox pair concentration. We ascribe this effect to the regeneration of the oxidized dye by iodide, in this way screening the positive charge from possible recombination with injected electrons and leading to a prolonged decay.