A Self-Powered p-CuO/n-Si Heterojunction-Type Ultraviolet Photodetector

Abstract

A self-powered p-CuO/n-Si ultraviolet (UV) photodetector (PD) operating without a bias voltage was prepared by using femtosecond (fs) laser direct writing and magnetron sputtering coating technology. A large area of randomly distributed nanopore structures (NPs) was induced on the n-Si surface by a fs laser, enhancing light absorption. A p-CuO nanofilm was sputtered on a fs-laser treated Si surface to construct a PD with a heterojunction region. The PD with NPs (CuO/NPs-Si PD) exhibits exceptional performance at zero bias, with an ultralow dark current (∼4 pA) and a photogenerated current (2.5 nA) under 365 nm UV illumination (5 mW/cm²), achieving an impressive current response ratio of ∼639.25. In contrast, the untreated CuO/Si PD shows no stable photocurrent, highlighting the critical role of laser-induced NPs. The device exhibits selective UV sensitivity, with an optimal response at 365 nm compared to other wavelengths at the same light intensity. The comparison between CuO/NPs-Si and CuO/Si PDs demonstrated that the former has good response, practicality, and repeatability due to the incorporation of NPs on the n-Si surface. These structures increase the adsorbable specific surface area of p-CuO, thereby further enhancing the photovoltaic effect. The detector is simple to prepare and has minimal dark current noise and high photogenerated current switching ratio. The fs laser-induced NPs eliminate the transient sharp peak currents dominated by the pyroelectric effect of the sensor. Furthermore, the introduction of a silicon substrate also improves the possibility of device-integrated application. Structural features and UV detection performance of the device determine its potential application prospects.