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Electrochemical Impedance Spectroscopy Characterization of Electron Transport and Recombination in ZnO Nanorod Dye-Sensitized Solar Cells

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journal contribution
posted on 18.06.2009, 00:00 by Chuan He, Zhi Zheng, Huili Tang, Linan Zhao, Fang Lu
In this work we carried out electrochemical impedance spectroscopic (EIS) characterizations on a ZnO nanorod dye-sensitized solar cell to investigate its electron transport and recombination properties and how these properties influence the cell performance. It is shown that the recombination process in the cell is mediated by an exponential distribution of surface trap states on the nanorods, which also governs the capacitance of the nanorods at low potentials. A strong dependence of recombination on the existence of a constant illumination has been observed, and this is shown to be a major efficiency-limiting factor for this type of devices. The Warburg feature has been observed from the high frequency region of the impedance, and transport resistances of ∼100 to 67 Ω have been determined. The transport resistance shows no dependence on illumination.