Continuous time random walk simulation of short-range electron transport in TiO2 layers compared with transient surface photovoltage measurements

The study of electron transport by transient surface photovoltage (SPV) measurements, in compact and nanoporous TiO2 layers sensitized with dye at the outer surface, is summarized, extending previous results with continuous time random walk (CTRW) simulations in order to account for energy dispersion in the observed electron diffusion. In the case of nanoporous layers anomalous diffusion is observed immediately after electron injection for a wide temperature range, and the diffusion is consistent with an exponential distribution of traps that is affected by temperature variations. In the case of short-range diffusion in ultrathin compact TiO2 layers, followed by electron recombination with the oxidized dye molecules, numerical simulation of electron transport with exponential distribution of traps with the CTRW approach provides an accurate description of the main features and time scales of the observed decays.