Hierarchical hybrid microarchitectured 3D/1D titanium oxide (TiO 2 ) films were developed by one-step surfactant-free hydrothermal method over TiO 2 seeded FTO substrates. The TiO 2 films synthesized from hydrothermal method at growth temperature 180 °C were dried at room temperature and then heat treatment at 70 °C, 150 °C, 250 °C, 350 °C and 450 °C formed hierarchical hybrid microarchitectural structures. X-ray diffraction and Raman spectral results of the prepared TiO 2 hierarchical hybrid microarchitectured films confirmed the formation of single phase rutile tetragonal TiO 2 system. Scanning electron microscopy results revealed that the heat treatment at various temperatures effectively modified the surface morphology of hydrothermally grown 3D/1D TiO 2 hierarchical hybrid microstructures. The UV–vis and photoluminescence spectral results of the heat treated TiO 2 films revealed modification in the bandgap energy and the electron-hole pairs recombination rate respectively when compared with that of the pristine film. The photoelectric measurements revealed that the heat treated film at 450 °C exhibited the relatively higher photocurrent density of 2.68 mA/cm 2 and applied bias potential efficiency of 2.91% as compared with all other heat treated and pristine films. [ABSTRACT FROM AUTHOR]