Study Of Self-powered Ultraviolet Photodetector Based On NiO

The ultraviolet photodetector converts the ultraviolet light signal into a current signal to realize the detection of light.They are widely used in environmental monitoring,flame detection,satellite communication,missile plume detection,biology and astronomy.Self-powered ultraviolet photodetector can detect ultraviolet light without external power supply,meet the needs of the next generation of nano-devices with small size,light weight,low power consumption and integration.In the field of in-situ medical treatment monitoring and remote environment detection has a wide range of applications.At present,the photo responsivity and response speed of self-powered ultraviolet photodetectors need to be further improved.NiO and TiO₂have small lattice mismatch and similar width of forbidden band,and they are also have good light absorption in the ultraviolet region.So they can construct a type II heterojunction to realize self-powered ultraviolet light detection.The process of generation,separation,transmission and collection of photo-generated carriers in the NiO/TiO₂heterojunction determines the performance of the detector without an applied electric field.In this paper,NiO is deposited on a one-dimensional TiO₂nanorod array.By adjusting the NiO energy band structure and the photogenerated carrier transmission path,the photogenerated carrier separation and transmission capabilities are improved.It mainly includes the following two aspects:1.The built-in electric field is the driving force for the separation of photogenerated carriers in the NiO/TiO₂heterojunction.By changing the thickness of the NiO nanosheets and films deposited on the surface of the TiO₂nanorod array,the position of NiO Fermi level,the hole concentration,and the carrier transmission path are adjusted to enhance the built-in electric field of the heterojunction and improve separation and transmission of the photogenerated carriers and the ability of electrodes to collect carriers.The self-powered NiO（5h）/TiO₂heterojunction device has a photo responsivity of 0.86 A/W,a detection sensitivity of 1.6×10¹³Jones,and a response time of 3 ms.2.Heterojunction interface barrier will affect the photo-generated carrier transfer.Using magnetron sputtering method deposited NiO nanocrystalline film on the surface of TiO₂nanorod array,by controlling the sputtering power,the crystal quality of NiO is changed,the position of the NiO Fermi level is adjusted,reducing the NiO/TiO₂heterojunction interface barrier and interface carrier recombination,the defect state and the transfer resistance of the heterojunction interface are reduced,and the photogenerated carrier transfer ability is improved.The NiO（80W）/TiO₂heterojunction device has a photo responsivity of 74 m A/W and a response time of 34ms at 0 V bias.