The photoelectrochemical properties of nanostructured, porous WO3 films deposited by screen printing have been characterized by steady-state and small signal modulation methods as a function of film thickness. Monoclinic WO3 with a wide particle size distribution between 50 and 500 nm was synthesized by a very simple method, via the dehydration of tungstic acid. Related to the open morphology and relatively large feature sizes, the optimal thickness for light harvesting and current collection is about 12 mu m for front-side and about 20 mu m for backside illumination. Intensity-modulated photocurrent spectroscopy (IMPS) shows that the rate constant for charge transfer to the electrolyte solution is larger than that for surface recombination in most of the applied potential range, illustrating the promise of the material. However, charge collection is found to be an important process that can limit the photocurrent, especially for thicker electrodes in the photocurrent onset potential region. (C) 2017 Elsevier Ltd. All rights reserved.