ON THE MODELING OF THE DYE-SENSITIZED SOLAR-CELL

A simplified electric model of the dye-sensitized electrochemical sola r cell (DSC) is presented. It permits the calculation of internal stea dy-state cell characteristics like particle density distributions or t he electric field as a function of the (measured) external current I-e xt. The cell is modeled as an one-dimensional pseudo-homogeneous mediu m of thickness L, where all the electroactive particles involved in th e current supporting process move according to different effective tra nsport coefficients (i.e. effective diffusivities D and effective mobi lities mu). The electroactive particles are the electrons e(-) injecte d into the nanoporous TiO2 layer after light absorption by the dye, th e reduced and the oxidized counterpart of the redox electrolyte El(Red ) and El(Ox), and the positively charged cation Kat(+) being brought i nto the cell together with the electrolyte. By applying the continuity equation, the transport-equation and Poisson's equation to all the el ectroactive species involved (e(-), El(Red), El(Ox), and Kat(+)) and b y assuming a linear Boltzmann relaxation approximation for the back re action, a system of differential equations is derived, describing part icle densities, particle currents and the electric field within the ce ll. The underlying simplifying assumptions as well as the resulting li mits of the model are stated, and some possible extensions are given. This paper aims to outline the general ideas and limitations of the pr oposed electric modeling, numerical calculations have been successfull y implemented, but will be presented in a future paper. (C) 1998 Elsev ier Science B.V. All rights reserved.