Transparent ultraviolet photosensor based on vertically aligned ZnO nanorods: The role of the electrode geometry

Ultra-violet (UV) photosensors are commonly used for environmental monitoring and space applications to measure UV radiation in order to mitigate its negative effects. This work investigates the effect of the spacing between the electrodes on the performance and response of UV photosensors. First, ZnO nanorods are thermally grown on a glass substrate with transparent interdigitated electrodes. The surface topography and morphology are characterized using advanced microscopy techniques. The optical properties are explored using UV-Vis and photoluminescence analyses. I-t and I-V measurements in the dark and under UV radiation are carried out to reveal the photosensor characteristics at electrode spacings of 50, 75, 100, 125, and 150 µm. The best photosensor performance is observed at a spacing of 75 µm under a bias voltage of +7 V. The photosensor has a responsivity of 5.06478 mAW⁻¹, photosensitivity of 0.58002 %, gain of 1.0058, rise time of 0.533 s, and decay time of 0.474 s. Regardless of the performance of the photosensors, this study gives an insight into the role of the electrode geometry, including the electrode gap and measurement path, which could be helpful in designing UV photosensors and optimizing their performance.