Porous and dense nanocrystalline TiO2 films grown on F:SnO substrates used in vertical geometry ultraviolet photodetectors are investigated. Compared with a detector with a dense nanocrystalline TiO2 film (D-detector), a detector with a porous nanocrystalline TiO2 film (P-detector) exhibits one order of magnitude higher responsivity due to a light scattering effect. In addition, the vertical geometry detectors show a fast response time. The rise time and decay time of the P-detector and D-detector are 19 and 136 ns, and 14 and 100 ns, respectively, which are six orders of magnitude faster than those of lateral geometry detectors based on dense nanocrystalline TiO2 films. It is a result of a decreased mobility fluctuation. (C) 2012 Elsevier B.V. All rights reserved.