Light scattering of nanocrystalline TiO2 porous film with a double layer structure is studied by computer simulations in terms of four-flux radiative transfer model. Efficient light scattering in the double layer film composed of a transparent layer containing 10 run particles and a scattering layer containing a mixture of 10 and 150 nm particles is obtained by optimizing the film structure. An increase of the light absorption from the strong light scattering of the double layer film and the contribution of back reflection at the counter electrode leads to improve the total photocurrent density significantly. Limitation of the maximum total photocurrent density of the double layer film by the mass transport of the redox species is examined in virtue of the dependence of the diffusion limiting current densities on film structure under different diffusion coefficients of the redox species I-/I-3(-). (c) 2005 Elsevier B.V. All rights reserved.