Preparation And The Study Of Photosensitive Properties Based On ZnO Composites

Zinc Oxide?ZnO?is a new type of II-VI wide band gap?band gap 3.37eV?semiconductor material,with six-party zinite structure?lattice constant a=0.3249nm,C=0.5206nm?,its exciton binding energy is 60meV,greater than GaN?25meV?and ZnSe?22meV?,which makes the optoelectronic devices of the ZnO material to achieve efficient exciton composite luminescence even at room temperature.Therefore,ZnO is considered to be a promising photonic material in the blue UV region.ZnO materials can produce high quality single crystals at present,and can be extended by many methods,so that ZnO optoelectronic devices are more easily integrated.On the substrate,ZnO is rich in raw materials,cheap,non toxic,pollution-free,strong in radiation resistance and much lower in preparation temperature than other wide band semiconductors,which can greatly reduce the defects produced by high temperature preparation.Because of the quantum confinement effect of ZnO nanomaterials,these nanostructures often show better electrical characteristics than the bulk materials.Thus,it have been widely regarded as a third generation semiconductor material more potential than GaN in the field of short wave light electrical appliances.Graphene is considered to be the new generation semiconductor material in the future due to its unique physical phenomena,crystal and electronic structure.Compared with other carbon materials,graphene has larger specific surface area and unique structure.It has better mechanical,thermal,electrical and magnetic properties,and has high performance in nano electronic devices.It has extensive potential applications in the field of materials,field emission materials,gas sensors and energy storage.In the field of photoelectric,graphene has great potential:its electron mobility at room temperature is up to 2×10⁵cm²/?Vs?,higher than carbon nanotubes or silicon crystals,even more than most metals;the optical absorption rate of graphene is only 2%.Therefore,it is a very excellent transparent conductive material,which can be used as a light-emitting diode,solar cell,photodetectors and other photoelectric devices.Polymer PVK(N-vinyl carbazole,C₁₄H₁₁N),molecular weight 193.25.PVK is an organic semiconductor polymer that facilitates hole transport.Hole transport property is the best among many organic polymers.The highest occupied molecular orbitals?HOMO?and lowest unoccupied molecular orbital?LUMO?energies of PVK are-5.8eV and-2.3eV,respectively.PVK has good electrical properties,and its photoconductivity makes it can act as a photosensitive material for holography.PVK has strong blue emission excited state single peak and the peak value is about 420nm.PVK has been widely used as an electronic and optical material.This paper mainly consists of two aspects.One aspect is the fabrication of ZnO-rGO ultraviolet photodetector and the ZnO ultraviolet photodetector,another aspect is the fabrication of the ZnO-PVK heterojunction structure prototype device.The main contents and results are as follows:This part mainly consists of ZnO-rGO ultraviolet photodetector and ZnO UV photodetector.There are three difficulties in the study.The first is looking up a large number of documents and combining with the current situation in the laboratory to determine the experimental scheme;The second is the preparation process of ZnO-rGO composites;The third is the question of how to construct the two prototype devices of the ZnO-rGO ultraviolet photodetector and the ZnO ultraviolet photodetector.This part has successfully constructed ZnO-rGO UV photodetectors and ZnO UV photodetectors.The two ultraviolet photodetectors were characterized by IV.In comparison with the pure ZnO UV photodetector,the ZnO-rGO photodetector exhibits a much larger photocurrent and a better light-to-dark-current-ratio.The mechanism is studied in detail by using XRD,Raman,PL spectra,transmission spectra and photocurrent tests.The results show that the photocurrent enhancement is mainly because the carrier recombination was reduced by rGO.It provides a potential way to fabricate high-response UV photodetectors.This part mainly combines the n type ZnO semiconductor material with the organic semiconductor polymer PVK which is beneficial to the hole transmission,and wants to construct the prototype of the ZnO-PVK heterojunction device.The prototype of the ZnO-PVK heterojunction device is to break through two difficulties:one is the preparation process of one dimensional nano ZnO material with good conductivity;the second is to construct a ZnO-PVK heterojunction structure successfully and to test a good curve of rectifying curve.The work is mainly divided into two aspects:the preparation of ZnO-PVK composite and the construction and characterization of ZnO-PVK heterojunction structure.The difficulty of this part is that ZnO-PVK heterojunction should be successfully constructed and able to measure very good rectifying curves.This topic has been carried out all the time.Through the IV curve,it can be found that the light current of the ZnO-PVK heterojunction photodetector is larger than the dark current,which shows that the heterostructure has a certain detection effect.However,the rectifying curve has not been obtained.This is because the structure of the heterostructure has a certain detection effect,but it has not yet formed an effective barrier.Compared with the absorption curves of composite thin films and pure ZnO films,it is found that ZnO-PVK composite films have greater absorption intensity to ultraviolet light.Compared with ZnO thin films,the strength of PL spectra of ZnO-PVK composites decreased obviously.This indicates that there is an effective charge transfer between ZnO and PVK.In conclusion,an ultraviolet?UV?photodetector based on ZnO-reduced graphene oxide?ZnO-rGO?composites have been successfully fabricated.A pure ZnO photodetector was also fabricated by similar method.And the ZnO-PVK heterojunction photodetector with optical detection effect have been successfully constructed.These researches provide a potential method for the fabrication of high speed photo responsive UV photodetectors,which is of great significance.