Monte Carlo random walk simulation of electron transport in confined porous TiO₂ as a promising candidate for photo-electrode of nano-crystalline solar cells

Monte Carlo continuous time random walk simulation is used to study the effects of confinement on electron transport, in porous TiO₂. In this work, we have introduced a columnar structure instead of the thick layer of porous TiO₂ used as anode in conventional dye solar cells. Our simulation results show that electron diffusion coefficient in the proposed columnar structure is significantly higher than the diffusion coefficient in the conventional structure. It is shown that electron diffusion in the columnar structure depends both on the cross section area of the columns and the porosity of the structure. Also, we demonstrate that such enhanced electron diffusion can be realized in the columnar photo-electrodes with a cross sectional area of ∼1 μm² and porosity of 55%, by a simple and low cost fabrication process. Our results open up a promising approach to achieve solar cells with higher efficiencies by engineering the photo-electrode structure.