Defect-Assisted Broad-Band Photosensitivity with High Responsivity in Au/Self-Seeded TiO₂ NR/Au-Based Back-to-Back...

TiO₂ nanorods (NRs) have generated much interest for both fundamental understanding of defect formation and technological applications in energy harvesting, optoelectronics, and catalysis. Herein, we have grown TiO₂ NR films on glass substrates using a self-seeded approach and annealed them in H₂ ambient to modify their surface defects. It has been shown that broad-band photosensing properties of Au/self-seeded TiO₂ NR/Au-based two back-to-back Schottky junctions (SJs) for a broad wavelength of light are much superior as compared to those of the pristine and the control samples. Photoresponsivity values for the H₂-annealed sample are 0.42, 0.71, 0.07, and 0.08 A/W for detecting, respectively, 350, 400, 470, and 570 nm lights. Very low dark current and high photocurrent lead to a gain value as high as 1.85 × 10⁴ for 400 nm light. Unprecedentedly modified NR-based SJs show excellent photoresponsivity for detecting as low as 25, 36, 48, and 28 μW/cm² power densities of 350, 400, 470, and 570 nm lights, respectively. It is found that Ti³⁺ defects play a key role in an efficient photoelectron transfer from TiO₂ to Au. Our work, for the first time, highlights the simplicity and reveals the rationale behind the excellent properties of Au/self-seeded TiO₂ NR film/Au back-to-back SJs.