Positive and negative photoconductivity characteristics in CsPbBr/graphene heterojunction.

Broadband response photodetectors have received great research interest in optical sensing field. Usually, materials with positive photoconductivity (PPC) are general and the lack of negative photoconductivity (NPC) materials limits the application of photoelectric effect, especially in the broadband photodetecting field. Therefore, the finding of NPC materials is very important. Integrating PPC and NPC response into a single device is extremely meaningful to the development of broadband photodetector. In this work, we fabricated CsPbBr nanocrystals (NCs)-multilayered graphene heterojunction, which achieved persistent NPC response to ultra violet (300-390 nm) and PPC response to visible light (420-510 nm). The persistent NPC relies on the desorption of HO vapor, and varies its intensity with the power intensity of laser. The PPC relies on the holes transmission from NCs to graphene. The recombination of NPC and PPC effect provides background knowledge for the development of broadband photodetector.