Fabrication And Properties Of Photo-electro-chemical Ultraviolet Photodetector Based On TiO₂ Nanotubes

As one of the novel photovoltaic ultraviolet photodetectors?UVPDs?,the photoelectrochemical?PEC?UVPD has captured a great deal of attention in environmental monitoring,flame detection,chemical analysis and missile plume detection.Apart from exhibiting a high photosensitivity and fast photoresponse,the PEC UVPD also can work without a driving bias voltage,which means that the PEC UVPD can work free of external power source.In the last decade,various wide-bandgap semiconductors,such as ZnO,SnO₂ and TiO₂,have been widely investigated in the PEC UVPDs.In particular,TiO₂ has been extensively investigated for preparing the PEC UVPDs due to its key advantages:band gap?3.2 eV?,good chemical stability,high carrier mobility,radiation stability and high photoelectric conversion efficiency.However,because of the recombination of photogenerated electron-hole,the low quantum efficiency limits the performance of PEC UVPDs based on TiO₂.Once the noble metal modification and semiconductor heterojunction are combined,it is possible to get a high-performance UVPD.In this paper,TiO₂ nanotubes were prepared by liquid phase deposition?LPD?.Then,photo-deposition method was used to deposit metal Ag nanoparticles?NPs?on the surface of the nanotubes,and finally the ZnS layer was coated to prepare a PEC UVPD,and the performance of the ultraviolet detector of the device was studied.The specific research contents are as follows:Firstly,ZnO nanorods were prepared by hydrothermal method,and then TiO₂nanotubes were prepared at room temperature by liquid phase deposition method using ZnO nanorods as template.The elemental composition,microscopic morphology and crystal structure of the sample were analyzed by means of SEM,XRD.After the PEC UVPD was prepared,its detection performance was tested.Ultraviolet detection performance experiments show that the UVPD based on TiO₂ nanotubes has a fast response time.Secondly,on the basis of the prepared TiO₂ nanotubes,the metal Ag NPs were deposited on the surface of TiO₂ nanotubes by photo-deposition method.The metal Ag particles with different particle sizes were obtained by changing the irradiation time,and the Ag NPs were studied.The effect of Ag particles with different particle sizes on the detection performance of the UVPD based on TiO₂ nanotubes had aslo been studied.The experimental results show that the UVPD based on TiO₂/Ag nanotubes has the best performance when exposed to light for 2 minutes.Finally,the surface of TiO₂/Ag nanotubes was coated with different thicknesses of ZnS layer by SILAR method to investigate the effect of cycle number on the morphology of the sample.After preparing the UV detector,the effect of ZnS layer with different thickness on device performance were investigated.It is found that the UVPD based on TiO₂/Ag/ZnS nanotubes has the best performance when the cycle is five times.