High-Performance Carbon Nanodots/Graphene Heterojunction Solar-Blind Ultraviolet Photodetector via Vertical Structure

Abstract

The vertical-structure 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 nanodot (CND) has drawn great attention to be playing an essential role in absorbing solar-blind UV waves as the active layer of the PD. However, CND prepared for solar-blind UV PDs, independent of sophisticated manufacturing method and extreme process conditions, has yet to be well developed. Herein, for the very first time, a vertical structure CNDs/graphene heterojunction type solar-blind UV PD is introduced, where the CND and the graphene are used as the photosensitive layer and the transparent electrode, respectively. Particularly, the CND is fabricated with a low-cost and one-step electrochemical strategy. The device realizes an optimized performance tradeoff, presenting responsivity of 76.01 mA/W, normalized detectivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.17\times 10^{{10}}$ </tex-math></inline-formula> Jones, and rise/decay time of 0.54/0.27 s under the illumination of 1.47 mW/cm2 at 254-nm wavelength, along with the bias voltage of −5 V and the substrate voltage of 10 V applied. The results show that this work has unlocked the critical bottleneck of developing a graphene-based solar-blind UV PD with higher responsivity, greater detectivity, and shorter response time, unveiling the potential for missile warning, flame detection, and other areas of interest.