Low Power Graphene Photodetectors for Weak Light Detection

Dung-Sheng Tsai¹, Zan-Ming Bo¹, Yuan-Jin Lin², Ya-Yun Huang², Wei-Chen Tu^3*

¹Department of Electronic Engineering, Chung Yuan Christian University, Taoyuan City, Taiwan
²Program on Semiconductor Manufacturing Process Academy of Innovative Semiconductor and Sustainable Manufacturing, National Cheng Kung University, Tainan City, Taiwan
³Department of Electrical Engineering, National Cheng Kung University, Tainan City, Taiwan

* Presenter:Wei-Chen Tu, email:wctu@gs.ncku.edu.tw

Two-dimensional graphene composed of a one-atom-thick planar carbon sheet, has attracted much attention for applications in flexible devices because of its high mobility, broadband absorption, high flexibility, and high strength. High-performance graphene PDs have been proposed to detect incident light because of the internal field formed near the interfaces of metal electrodes and graphene ranging from UV to THz. However, most large-scale graphene is synthesized on Cu or Ni substrates by a high-temperature chemical vapor deposition (CVD) chamber, limiting applications of graphene-based devices. As a result, reduced graphene oxide (rGO) is considered a potential candidate for flexible electronics due to its low cost and mass production.

In the study, flexible reduced graphene oxide PDs with asymmetric Ag nanowires and Cu NWs electrodes through all-solution processes are proposed. We optimized the fabrication parameters for rGO layers to reduce the roughness of rGO films and improve the transportation of generated carriers. These flexible rGO photodetectors were characterized under weak-light environments. The photocurrent-to-dark-current ratio of rGO flexible PDs with asymmetric electrodes was enhanced compared to PDs with Ag NWs — Ag NWs and Cu NWs — Cu NWs symmetric electrodes. Additionally, we introduce negative photoconductivity (NPC) monolayer graphene photodetectors by chemical vapor deposition (CVD), and realize a positive photoconductivity (PPC) photodetector by decorating perovskite FAPbI3 quantum dots prepared by a simple and cost-effective non-polar solvent synthesis method on the graphene surface. The critical analysis for the different photoconductive mechanisms will benefit the development of future multifunctional systems and open the way of graphene and rGO PDs for low-cost consuming applications operated in a weak-light environment.

Keywords: graphene, photodetector, weak light