A high-performance NiO/TiO2 UV photodetector: the influence of the NiO layer position

Abstract

p–n Junctions have been widely used in the construction of high-performance TiO₂ ultraviolet photoelectric detector devices, especially NiO/TiO₂ heterostructures. In this work, two devices with different structures were constructed to investigate the effects of the growth of NiO above (S-TN) and below (D-NT) the TiO₂ array on the device performance, and the D-NT device showed better performance. The D-NT device exhibited a lower dark current, with a decrease of approximately an order of magnitude compared with S-TN PD and TiO₂ nanoarray (NA) PDs. The D-NT heterojunction device demonstrated a large on–off ratio of 5.4 × 10⁴, a high detection sensitivity of 1.44 × 10¹⁴ Jones, and a fast photoresponse time of 2 s under UV light illumination. Interestingly, the D-NT device also displayed self-powered performance, and its photoresponse time was 0.1 s. The dense and uniform NiO film deposited on the FTO substrate not only forms a built-in potential field with the TiO₂ NAs, but it also provides greater uniformity and stability to this built-in potential field compared to a NiO layer spin-coated on TiO₂ NAs, which may be the main reason for the high performance of the D-NT photodetector. The device in which NiO was grown below the TiO₂ array provides a fundamental basis for the future development of all-solid-state photodetectors.