Nanostructured Rutile TiO₂Films with (002) Texture Prepared by the Chemical Bath Deposition Method for Application in Photoelectrochemical Ultraviolet Detectors

Within the scope of this work, we present a simple ultraviolet photodetector based on a chemically deposited nanostructured TiO₂film. XRD and Raman spectrometry reveals that the TiO₂film is formed in the rutile phase. It consists of spherical particles with an average size of 25–30 nm, preferably aligned in the direction orthogonal to the (002)-plane. The films are electrochemically active in the photooxidation process of sulfite anions, showing an external quantum efficiency (EQE, Y) value of up to 89% at 305 nm. The analysis of photopolarization curves using the Gärtner equation demonstrates a photohole diffusion path equal to ∼550 nm, which is comparable to the film thickness. The films are used in electrochemical three-electrode photodetector designing. The detector exhibits 2 linear plots in light intensity-current dependency: one starting from 0.02 mW/cm²to 0.25 mW/cm²and another from 2 mW/cm²to 60 mW/cm². The photodetector shows responsivity up to 0.22 A/W, photosensitivity up to 360, specific detectivity up to 5.08 × 10¹¹cm·Hz^1/2/W and an on/off rate of 120/300 ms. The high efficiency of the detector is determined by three factors: reduced recombination of charge carriers due to the (002)-oriented growth of the rutile film, the high quality of contact between the semiconductor and substrate, and the application of an aqueous solution of sodium sulfide as an electrolyte. The combination of these factors results in high values of spectral responsivity along with a low value of dark current.