Study On The Performance Of Self-driving Electrochemical Ultraviolet Photodetectors Based On TiO₂ Nanorode Arrays

In recent years,as the nanomaterials and electronic technology are in the ascendant,ultraviolet photodetection field has also developed rapidly.The ultraviolet photodetectors(UVPDs)with excellent photoelectric performance have gradually been extensively applied in military and civilian fields.Electrochemical ultraviolet photodetectors(EUVPDs)based on one-dimensional TiO2 nanostructures,as a new type of liquid junction photovoltaic detector,have drawn extensive attention,due to its relatively simple structure,low preparation cost,and long-term stability without any external bias.However,most self-powered EUVPDs are based on 1-D TiO2 nanostructures,which often lack an effective mechanism for separating electron-hole pairs.As a result,the interface charge recombination rate is relatively high.Moreover,the detection performance of self-powered EUVPDs,including responsivity,sensitivity,spectral response range and long-term stability,is still need to be further improved,.In view of the above problems,this thesis used the TiO2 nanorod arrays(TNRAs)as the main material and managed to further improve the comprehensive performance of photoelectric response and expand its application range by means of self-doping,surface modification and structural optimization.The main research work and innovations are summarized as follows:1.Using TNRAs as photoanode materials to enhance the photoelectric response performance of EUVPDs.Ordered TNRAs were synthesized by one-step hydrothermal method and then performed annealing treatment in reducing atmosphere(argon),thereby introducing Ti3+ and OVs defects in the TiO2 lattice and forming energy levels of defect states with the self-doping effect.It can’t only effectively increase the carrier concentration in the semiconductor materials,but also improve the photoconductivity of photoanode materials in favour of the rapid transport and segregation of photogenerated carriers at the electrode/electrolyte interface.In addition,the circular regeneration of redox couples in electrolyte was also accelerated,which was ultimately contributed to a huge increase in the photoresponse current of the device.2.The ZrO2@Ar-TNRAs heterostructure were used as the photoanode materials to improve the photoelectric response performance of EUVPDs.The ZrO2@Ar-TNRAs composite structure can facilitate the effective segregation of photogenerated carriers and impede the direct recombination of photogenerated electrons with S2’ in the electrolyte to a certain extent,resulting in enhancing the photoelectric response performance of the device.Finally,the best ZrO2@Ar-TNRAs(S2)samples for sensitization time were obtained.3.By optimizing and improving the device structure and packaging form,the photoelectric response performance of EUVPDs was further enhanced.First of all,Pt was used as the counter electrode of the device,which can’t only play a good catalytic effect on the redox reaction that occurred inside the device,but also reflect a part of the incident light,leading to effectively enhancing the utilization efficiency of the incident light and improving the photoelectric response of the device.Secondly,compared with sulfur-based aqueous solutions,the selection of iodine-based organic electrolytes can effectively inhibit the process of photolysis water to produce hydrogen.Therefore,the long-term stability of the device was greatly improved.Finally,compared to the traditional packaging form,the packaging structure in which the photoanode and the counter electrode were in close contact can greatly shorten the distance between the two electrodes.As a resut,while increasing the carrier transport rate,it also reduced the recombination possibility of photogenerated carriers,which promoting the further increasement in the photoresponse current.4.The metallic single-walled carbon nanotubes(m-SWCNTs)were modified on the surface of the ZrO2@Ar-TNRAs composite structure to further improve the comprehensive photoelectric response performance of EUVPDs.The SWCNTs can be interwoven with TiO2 nanorods to form a 3-D conductive network structure,which can greatly enhance its ability of light trapping.In addition,the SWCNTs with good conductivity can also be used as a hole transport carrier,which greatly facilitated the segregation and rapid transport of photogenerated carriers,and the sufficient reactive sites on the surface of SWCNTs can also provide a strong guarantee for the cyclic regeneration of the redox pairs.What’s more,considering the surface plasmon resonance effect,the m-S WCNTs can absorb a part of visible light and produce the hot electrons with high energy,which can directly transition to the conduction band of TiO2,further increasing the carrier density inside the materials,Finally,the UV-visible photoelectric response performance of the device was significantly enhanced,and the response band range of the device was also expanded.The best photoresponse current density of EUVPDs based on SWCNTs/ZrO2@ArTNRAs samples with I-/I3-as the electrolyte and Pt as the counter electrode studied in this paper can reach 7.14 mA/cm2,and the photoresponse is 158.67 mA/W,the on/off current ratio is 1.59 × 105,the specific detection rate is 3.17 × 1013 Jones(Jones=cm·Hz1/2/W),the quantum efficiency is 53.39%,and the light response time is 0.08 s.