Study On The Protective Layer Of Silver Nanowire Transparent Conductive Electrode For Photoelectrochemical UV Detector

Ultraviolet(UV)light comes from a wide range of sources,which is harmful to human skin and health.But it also plays an important role in production and life,often used in sterilization,stage decoration,ore identification,etc.Therefore,it is necessary to detect UV light.UV detector is a device which can convert UV signal into detectable signal.There are many kinds of it,such as thermal detector,photosensitive detector and photoelectric UV detector.These several types of devices have the disadvantages of low sensitivity,low detection efficiency and high cost respectively.Therefore,researchers have proposed a new photoelectrochemical(PEC)UV detector,which is a sandwich structure of liquid junction device.At present,the research on PEC UV detectors is mainly focused on photoanode,which mainly includes different kinds of semiconductor materials(such as SnO2,ZnO,etc.)and different structures(such as nanoparticles,nanospheres,nanotubes,nanorods and nano-branches,etc.).In these studies,the photoanode conductive electrodes are all based on FTO/ITO,but this kind of transparent conductive electrode composed of wide-band gap semiconductor oxides has serious UV filtering problems.When they are used as conductive substrates,devices cannot detect UV light below 300 nm and only have optical response in the wavelength of 300-400 nm,severely limiting the detector’s application in the broad-spectrum UV range.The key to solve this problem is to make the conductive electrode can pass through UV light below 300 nm and have good conductivity.This thesis mainly studies the following three aspects:① Improving the performance of silver nanowires(AgNWs)by transparent conducting electrode(AgTCF)and TiO2 protective layer with different structures;② Broadening of response range of PEC UV detector based on AgTCF and conductive electrode containing TiO2 protective layer;③ Enhancement of CuO/TiO2 heterojunction protective layer on PEC UV detector performance.The detection range of the traditional device is improved,and the principle that the protective layer inhibits the electron recombination reaction is analyzed.First,the study based on AgTCF and its protective layer.Polyvinylpyrrolidone(PVP)nanowires were first prepared by electrospinning.AgNWs were prepared by DC magnetron sputtering by using PVP nano wires as templates.AgTCF was obtained by transferring AgNWs to quartz.The photoelectric performance,thermal and mechanical stability of AgTCF were mainly tested and studied.The transmittance of AgTCF in UV and visible regions can reach more than 80%,the sheet resistance is as low as 2 Ω/sq,the melting point is about 375℃,and it has good mechanical stability.Then,two kinds of protective layers with different structures were prepared by magnetron sputtering.①T-AgTCF was obtained by directly sputtering TiO2 film on AgTCF.When the sputtering time was 6 min,the transmittance of electrode in UV region was 33.6%.② AgNWs network was used as the template to directly sputter TiO2 to obtain the conductive electrode CST-AgTCF with shell core structure,which had a very high transmittance in the UV-visible region(compared with AgTCF).The melting point of AgTCF was increased to 485℃(T-AgTCF)and 800℃(CST-AgTCF)respectively,and the mechanical stability was also improved.Secondly,three kinds of UV transparent conductive electrodes prepared in first part were applied to PEC UV detector photoanode.These three structures of the devices broaden the spectrum response range of the PEC UV detector and can detect UV signals below 300 nm.The maximum spectral responsivity of devices based on AgTCF was 2.96 mA/W,that based on T-AgTCF was 3.61 mA/W,and that based on CST-AgTCF structure was 4.40 mA/W.Thirdly,the heterojunction protective layer was prepared with two semiconductor materials,CuO and TiO2,by the two methods of preparing protective layer in the first part.When the sputtering time of both materials was 60 s,the peak responsivity of the device based on the CuO/TiO2 protective layer was 5.30 mA/W.When the sputtering time of the mesh CuO/TiO2 protective layer was 120 s,the spectral response of the device was increased to 5.83 mA/W.This thesis mainly studies the above three parts,and solves the problem that the traditional conductive electrode(FTO/ITO)is not permeable to UV light and the serious composite between the photoanode and electrolyte.At the same time,this kind of conductive electrode based on metal nanowires provides a new idea for the study of the performance of photochemical devices(such as photochemical ultraviolet detectors,dye sensitized solar cells).Relevant research results provide a new theoretical basis for the study of carrier recombination and broadening the spectrum response range of devices.