Effect of V doping on the band-gap reduction of porous TiO2 films prepared by sol–gel route

V-doped TiO2 porous films had been prepared on glass substrates via sol–gel method using polyethylene glycol (PEG) as organic template. The model concerning the pore formation and change of the band-gap was discussed. The experiment results show that the porous structure can be obtained by phase separation caused by the chain change and self-assembly of PEG molecular. Sol concentration and PEG content have important roles in porous structure formation. Moreover, the band-gap presents a gradual decrease from 3.28 eV to 2.82 eV with the increase of the V doping content from 0 to 0.2 in V-TiO2 film.