Study On Self-powered Electrochemical Ultraviolet Photodetectors Based On Black TiO₂ Nanotube Arrays

In recent years,ultraviolet photodetectors(UVPDs)with excellent photoelectric performance have become more and more important in industrial production and scientific research.Traditional photoconductive UVPDs require an external power source to drive,which brings a lot of inconvenience to charging and replacing the power source under long distance and extreme environmental conditions.The photoelectrochemical ultraviolet detector not only can achieve self-drive,but also has strong environmental adaptability,and can achieve independent,autonomous,sustainable,and long-term work in a remotely controlled environment.Based on the current research on self-powered UVPDs of different materials and structures,how to further improve the photoelectric responsivity,optical response rate,and long-term stability of UVPDs are the focus of current research.The main research work and innovation of this article are as follows:(1)Use black titanium dioxide nanotube array(TNAs)as photoanode materials to improve the photoelectric response performance of UVPDs,An ordered anodized TNAs was prepared by electrochemical anodization,and black TNAs were prepared by annealing and reduction in an inert gas argon,thereby inducing oxygen vacancies(OVs)and Ti3+ defect state energy levels,which increases the donor electron concentration in the semiconductor material and improve the conductivity of the material,and the formed electron traps can suppress electron-hole pair recombination and contribute to the substantial increase in photoresponse current density.(2)Single-walled carbon nanotubes(SWCNTs)are modified on the surface of the photoanode material to improve the photoelectric response performance of UVPDs.By modifying 0.1%wt SWCNTs on the surface of TNAs,which can incident photons be scattered and absorbed multiple times,enhancing light capture effect and excitation to generate surface plasmon effect.The built-in potential generated at the SWCNTs/TNAs contact interface can promote the separation of electron-hole pairs and carrier transport.SWCNTs with high specific surface areas also act as hole acceptors to accumulate photo-generated holes,providing sufficient active reaction sites for redox substances,thereby enhancing photoresponse performance.(3)Improve the packaging form of photoanode and counter electrode to enhance the photoelectric response performance of UVPDs.Compared with the traditional device packaging structure,the packaging structure of the photo-anode and counter electrode of UVPDs in close contact not only shortens the distance between the two electrodes and reduces the carrier recombination rate,but also forms a porous channel electrochemical reaction array structure that enables the carriers to migrate directionally,thereby increasing the carrier transmission rate.The photoresponse current density of UVPD based on SWCNTs/black TNAs with S2-/Sx2-as the electrolyte studied in this paper can reach 133.5 ?A/cm2,the photoresponse is?60 mA/W,and the on/off current ratio is?4.3�103,the rise time of the light response time is 4 ms,and the decay time is 27 ms.The maximum photoresponse current density of UVPD based on SWCNTs/black TNAs/I-/I3-can reach 159.7 ?A/cm2,which is a further 19.6%improvement over UVPD with S2-/Sx2electrolyte.