Computer simulations of light scattering and absorption in dye-sensitized solar cells

The TiO2 electrode of dye-sensitized solar cells (DSC) consists of 10-30 rim sized particles which are sintered together. The effective surface of the TiO2 electrode is increased up to 1000 fold by the nanoporous structure. It is covered with a layer of dye, so an acceptable overall absorption can be achieved. The absorption in the cell, and therefore the current, can be further enhanced by light scattering in the electrode. However, as larger particles are needed for effective light scattering, there will be the simultaneous effect of a decreasing effective surface. Computer simulations will be presented which show how the absorption can be increased by optimizing the size of the TiO2 particles. Starting from Mie theory applied to coated spheres, multiple scattering is calculated using a numerical solution of the radiative transfer equation. Certainly, the particles are sintered together and the assumption of independent scattering is not valid, but the qualitative results should still remain valid. These calculations predict that a suitable mixture of small particles, which result in a large effective surface, and of larger particles, which are effective light scatterers, have the potential to enhance solar absorption significantly. Furthermore, electrodes made of multiple TiO2 layers are investigated, each layer consisting of particles of different sizes. (C) 1998 Elsevier Science B.V. All rights reserved.