A Vertical Structured Solar-blind Ultraviolet Photodetector Based on the Carbon Nanodot/Graphene Heterojunction

The vertical structured heterojunction has been highlighted as a promising candidate for the solar-blind Ultraviolet (UV) Photodetector (PD) due to the control of its channel length and the strong electric field induced high carrier mobility. Meanwhile, Carbon Nanodots (CNDs) have drawn great attention to be playing an essential role in the active layer of the PD. However, CND based solar-blind UV PDs, independent from sophisticated manufacturing method and extreme process conditions, has yet to be well developed. Herein, for the very first time, a vertical structured CNDs/graphene heterojunction type solar-blind UV PD is introduced, in which the CNDs is used as the photosensitive layer and the graphene is used as the transparent electrode, implemented with a low-cost and low-complexity fabrication strategy of CNDs. The device exhibits extraordinary responsivity of19.11 mA/W, normalized detectivity of $4.60\times 10^{10}$ Jones and on/off ratio of 342 at low bias voltage of -5V under the illumination of1.5 mW/cm2 by 254 nm wavelength. The results show that this work has unlocked the critical bottleneck of developing a solar-blind UV PD with higher non-solar-blind ultraviolet signals rejection ratio, higher responsivity, and detectivity, unveiling the potential for missile warning, flame detection, and other areas of interest.