A Photoelectrochemical Type Self-powered Ultraviolet Photodetector Based On GaN Nano Materials

Ultraviolet?UV?light like a double-edged sword,UV has good application in sterilization,radiation curing,anti-counterfeiting and detection,but long-term exposure to ultraviolet light irradiation,prone to skin cancer and damage to health.UV detector can be used in military and civilian aspects,such as remote control,fire detection,environment monitoring and biological analysis and so on.There are more and more studies on UV detector,photoconductive UV detector requires additional power,easily influenced by the external environment and has a continuous photoconductive phenomenon.With the development of UV detector,pn junction and schottky UV detector are appear,which without additional power supply,but their demand to the preparation process of the device and the requirement for the quality of materials are extremely high,all of that leads to the high cost and it is very difficult to mass production.The self photoelectrochemical type ultraviolet detector arouse scientists' attention,because of its low cost,simple preparation technology,fast response speed,and the advantages of the strong sensitivity to UV light.In order to achieve superior performance of the self photoelectrochemical UV detector,the study of this thesis focused on light anode,mainly based on broadband gap semiconductors GaN materials,mainly to improve the UV absorption,improve the life of carrier and speed up the electronic transmission:As is known to all,GaN is direct wide band gap semiconductor,with the strong radiation resistance and good chemical stability,GaN has good application in visible light blind ultraviolet detector.First,we prepared GaN nanoparticles using the method of direct ammunition reduction,then prepared nanoporous films on FTO by drop drying method.Comparing the performance of UV detectors,we found that with the increase of annealing temperature,GaN crystalline nanoparticles are better and the performance of the detector is better.Secondly,we use TiO₂ modified GaN nano porous film in order to get excellent performance.As a result of the TiO₂ coating,the formation of heterojunction makes the pair of electron-hole separating quickly,the response reached 0.315 A/W,response time is less than 0.03 s,short circuit current density is 152.2 ?A cm^-2.In order to further improve the performance of the detector,we successfully achieved GaN nanowires by electrospinning,nanowires are mm magnitude and the diameter is uniform about 50 to 60 nm.And assembly based on GaN NWs self photoelectrochemical UV detector,nanowire can provides direct transport channel for electronic,speed up the electronic transmission.Comparing the performance of based GaN NWs photoelectrochemical ultraviolet detector with based GaN nano porous films photoelectrochemical ultraviolet detector,the performance has improvement,light response sensitivity slope is 0.27,68.8% higher than GaN nano porous film.we prepared GaN nanorods by hydrothermal synthesis,and nanorods are uniform,the length can reach a few microns.Nanorods can also provide direct transport channel for electronics,and the nanorods structure is more stable than nanowire.The short circuit current density of based on GaN nanorods photoelectrochemical ultraviolet detector is 24.2 ?Acm^-2.The short-circuit current density value of the GaN nanorods based UV sensor is 138% higher than that of the GaN NWs film.The response to the current density of light sensitivity is 0.52.