The mechanisms of electron transport and back-reaction in dye-sensitized solar cells (DSCSs) are investigated by intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS). The DSCSs with and without TiCl4-treated nanoporous TiO2 films are measured by IMPS/IMVS. The results indicate that the electron lifetime (n), the diffusion coefficient (Dn), the diffusion length (Ln), the incident photon to current efficiency (IPCE) and the photoinduced charge (Qoc) increase markedly, while the dark current and the electron transit time (d) decreases for the TiCl4-treated nanoporous TiO2 films. The influence of TiCl4-treatment of nanoporous TiO2 film on the electron generation, the transport and the recombination processes is investigated at a microscopic level.