High performance charge-transfer induced homojunction photodetector based on ultrathin ZnO nanosheet

Nanostructured zinc oxide (ZnO) semiconductors have emerged as promising materials for high-performance photodetectors due to their natural direct bandgap and extraordinary physicochemical properties. However, the oxygen vacancy defects of nano-ZnO can easily trap oxygen molecules in air and generate charge transfer at the interface, which induced continuous photoconductance that limited the development and application of ZnO in photodetection. Here, we demonstrate a homojunction ultrathin ZnO nanosheet photodetector with high performance and propose a better dominant photoresponse mechanism of the ZnO nanosheet driven by the charge transfer induced local field. The strong localized electric field significantly accelerates the separation of photo-generated carriers and effectively suppresses the dark current. Thus, the photodetector of the charge transfer induced homojunction exhibits ultralow dark current (10 ^-12 A), ultra-high specific detectivity (up to ∼10 ¹⁴ Jones), and fast rising (300 ms) and decaying times (310 ms), taking advantages of high-performance and fast response speed and subverting the limitation of traditional ZnO photodetectors in the field of application. An easy-fabrication, fast response, and high-performance photodetector proposed here provides a good paradigm for the next-generation photodetectors based on two-dimensional nanostructures.