Polarization losses in Gratzel solar cells with a porous anode

Polarization losses under the redox reaction on the anode and cathode in the iodine electrolyte of a Gratzel solar cell are considered. It is shown that the value of the maximum cell current is bounded by the diffusion transfer of ions on the cathode or anode, depending on the electrolyte composition. It is demonstrated that the value of polarization losses for a nonporous anode is determined by a linear Tafel law, whereas for a porous anode it is determined by the obtained nonlinear Tafel law that yields half as much polarization loss, according to Zeldovich theory. Operating conditions of Gratzel cell with a porous anode of finite thickness, under which the nonlinear Tafel law is realized for polarization losses, are considered.