Monte Carlo Random Walk Simulation of Electron Transport in Dye-Sensitized Nanocrystalline Solar Cells: Influence of Morphology and Trap Distribution

Electron transport in the porous nanostructured titanium oxide, as a main concern in the dye-sensitized solar cells, was investigated by random walk simulation. Geometrically disordered nanoparticle networks with random distribution of energy was generated and utilized for simulations. Dependency of the diffusion coefficient (D-ef) on the nanoparticles size, grains connectivity, and the network porosity was completely studied in two cases: traps are placed mainly on the surface or in the volume of the nanoparticles. It was shown that the D-ef is independent of nanoparticle size for both surface and volume diffusion. We have shown in this study that increasing the D-ef with the particle size is a consequence of the trap-filling (electronic) effect and not a geometrical effect. The role of electronic effect in electron transport in nanoporous materials has been highlighted in this work.