Layers of crystalline TiO2 were prepared using aerosol spray pyrolysis at different deposition temperatures and times. The effects of the deposition parameters on the structural, morphological and optical properties were investigated. The extent of the crystallinity and surface morphology of TiO2 depended very much on the growth temperatures. At a gas flow rate of 51/min, an inhomogeneous morphology with a cauliflower-like feature was observed for the films sprayed at 375 degrees C whereas they became denser and homogenous with the quality of both crystallization and diameters becoming better when the sprayed temperature was being increased up to 450 degrees C. The optical band gap of the TiO2 films was found to decrease from 3.66 to 3.61 eV as the film thicknesses was increased from 80 to 450 nm. The refractive index for electromagnetic waves having wavelengths between 450 and 800 nm varied between 2.0 and 2.12 for the films with thickness of 250-360 nm. There was a significant decrease to 1.93 when the thickness of the films was 450 nm. A layer of the sprayed-on TiO2 was then used as the hole-blocking layer in an organic-inorganic CH3NH3PbI3 perovskite based solar cell. A state-of-the-art transmission electron microscopy (TEM) technique for sample preparation was carried out using a dual focused ion beam (FIB) to investigate vertical morphology of the devices. It was found that the devices having the optimized thickness of the sprayed-on TiO2 displayed the power conversion efficiency (PCE) of 6.24%. (C) 2016 Elsevier Ltd. All rights reserved.