AN ELECTRICAL MODEL OF THE DYE-SENSITIZED SOLAR-CELL

An electrical model of the dye-sensitized solar cell (DSC) is presente d, which relates material parameters to cell performance. Based on the se parameters, the model permits the calculation of steady-state prope rties as e.g. internal currents or particle densities and the complete I-V characteristic of a DSC. The eel is modelled as a pseudo-homogene ous effective medium, consisting of the nanoporous TiO2 semiconductor, the light-absorbing dye and the redox electrolyte, which an intermixe d. Continuity and transport equations are applied to all the charge ca rriers involved: the electrons in the TiO2 conduction band, and the io dide, triiodide and cations of the electrolyte. The macroscopic electr ic field, resulting from the unbalanced charge-carrier distribution un der illumination, is calculated using Poisson's equation. The front an d back cell boundaries are modelled as an ohmic metal-semiconductor co ntact and as a redox electrode via a current-overpotential equation, r espectively. One of the main simplifications of this model is the cons ideration of only one-electron loss mechanism: the relaxation from the TiO2 conduction band to the redox electrolyte. This allows a direct c oupling of photon absorption with electron injection. The model is des cribed in detail, and exemplary numerical results are presented, which demonstrate the feasibility of the model. The influence of the most i mportant material parameters, such as electron mean lifetimes and mobi lities. on the cell performance are illustrated. (C) 1998 Elsevier Sci ence B.V. All rights reserved.