Preparation And Properties Of The Photoelectrochemical Photodetectors Based On Two-dimensional Materials

Traditional photodetectors based on inorganic compound semiconductor materials such as silicon have been applied in various aspects of biomedicine,environmental monitoring,military and security due to their characteristics of fast light response speed and high stability.However,they are still limited in the development space due to their narrow-band absorption,low spectral utilization rate,complex technology,expensive cost and high working voltage.Photoelectrochemical(PEC)photodetector as a new type of photodetector,the electron-hole pair generated by light excitation has reversible redox in electrolyte solution.thus,the photoelectric performance conversion can be promoted.In addition,the advantages of wide spectrum absorption,reasonable price,simple process and low operating voltage can make up for the shortcomings of traditional photodetectors in practical applications.Transition metal chalcogenides such as Tin(Ⅱ)sulfide(SnS),rhenium disulfide(ReS2)and niobium diselenide(NbSe2),are emerging as two-dimensional materials,the large specific surface area and effective interlayer charge transfer characteristic of the nano-lamellar structure are helpful to improve the photoelectric conversion ability and become the first choice of photoanode materials.At the same time,with the development of wearable and flexible portable electronic devices,flexible photodetectors have received more and more attention and research.Therefore,in order to solve the problem of electrode material flexibility and electrolyte leakage,the PEC photodetector was first prepared by photoelectrochemical technology,on the basis of this structure,a flexible PEC photodetector was fabricated by using flexible photoanode,and a portable solidstate PEC photodetector was successfully fabricated by using solid-state electrolyte and sandwich-like structure.the main tasks are as follows:(1)The PEC type photodetectorPEC photodetectors based on SnS have been fabricated by Physical vapor deposition method on rigid ITO conductive substrates.The results show that the photocurrent density of SnS photoanode increases with the increase of the thickness of the nano-sheet,through the test and analysis of its stability,sensitivity,light absorption performance and detection rate,it is proved that the PEC photodetector based on SnS can achieve high photocurrent density(1.82 μA/cm2)and bloom response(16.34 μA/W).(2)The flexible PEC type photoelectric detection based on heterogeneous structureIn this chapter,the flexible PEC photodetector was successfully fabricated.The flexible photoanode was prepared by liquid-phase stripping method,and the nano-film was electrodeposited on the flexible conductive substrate.Because the electrical conductivity of the flexible substrate is not as good as that of the rigid substrate,which may affect the photoelectric performance,so the heterostructure is chosen to design the photoanode in this chapter.First,a flexible heterojunction anode was prepared by using the metal Ti3C2 Extrinsic semiconductor ReS2.The results showed that:①The photoelectrical properties and flexibility of the anode were better than those of pure ReS2(1.69 μA/cm2),the successful fabrication of ReS2/Ti3C2 heterojunction(2.06 μA/cm2)can obviously improve the photoelectric conversion performance of the detector;②The photocurrent density(2.09 μA/cm2 to 1.79 μA/cm2)changed little at different bending cycles(0,100,200 and 300 cycles),showing good flexibility;③ The photocurrent density(2.06 μA/cm2 to 0.98 μA/cm2)decreased at different bending angles(0,15,45,60 and 75°),it may be caused by some sample falling off(the reduction of light area)during the bending process.Secondly,the Nb2O5 oxide film was produced by the self-passivation of NbSe2,and the oxide-doped Nb Se2/Nb2O5 heterojunction flexible photoanode was prepared,which helps to protect or reduce sample shedding and maintain bloom response performance.The results of flexible measurement show that:①The different sizes of the nanoplate photoanode are obtained at different centrifugal speeds(1000,3000,5000 and 7000 r/min);The photocurrent density values(1.75 μA/cm2,2.21 μA/cm2,2.23 μA/cm2 and 1.88 μA/cm2)are also different,which proves to some extent that the larger specific surface area of the nano-chip can improve its photoelectric conversion characteristics;②The photocurrent density at different bending angles(0,15,45,60 and 75°)was relatively stable(～2.32 μA/cm2);③the test results at different bending cycles(0,100,200 and 300)were also relatively ideal.(3)The solid-state flexible PEC type photoelectric detection based on heterogeneous structureThe solid-state flexible PEC photodetector was fabricated according to the requirements of the practical application for the portability and high integration of photodetector.Firstly,a flexible photoanode based on oxide-doped Nb Se2/Nb2O5 heterojunction was prepared,secondly,the liquid electrolyte was replaced by solid electrolyte to solve the problem of electrolyte leakage and volume,a sandwich-like detector is constructed by using a flexible conductive substrate based on hollow mesoporous carbon spheres as a pair of electrodes.The results show that the photocurrent density is stable(～0.13 μA/cm2)and flexible at different bending angles(0,15,45 and 75°).