Solution-Processed NiO/Si Heterojunctions for Efficient Self-Powered UV–Vis-NIR Broadband Photodetection

In the current work, efficient self-powered UV–vis-near-infrared (NIR) broadband NiO/Si heterojunction photodetectors have been fabricated by room-temperature spin-coating synthesis of a wide bandgap NiO nanocrystal thin film on an n-type Si substrate. Structural properties and atomic binding energy studies suggested that Ni vacancy defects were formed in the NiO nanocrystal thin films, verifying their p-type conductivity, which facilitated the formation of a p–n junction at the NiO/Si interface. Further studies showed that the energy band structure of NiO matched well with that of Si with a small valence band offset (0.04 eV) at the NiO/Si interface, facilitating the efficient transport of photoexcited carriers therein. As a result, responsivity and detectivity as high as 2.0 A/W and 8.5 × 1013 Jones, respectively, have been obtained at zero bias, both of which are higher than most reported state-of-the-art devices. Furthermore, the NiO/Si heterojunction photodetectors showed good stability and uniformity. Because of the simple process of spin-coating synthesis of NiO nanocrystal thin films, the fabrication of efficient and broadband NiO/Si heterojunction photodetectors is scalable, reproducible, and low cost, which will find applications in modern industrial and scientific applications.