Fabrication And Properties Of Photodetectors Based On Graphene And Perovskite Quantum Dots

Graphene is an attractive optoelectronic material for light detection because of its broadband light absorption and fast response time.However,the relatively low absorption cross-section,fast recombination rate,and the absence of gain mechanism have limited the responsivity of pure graphene-based phototransistor to?10^-2A·W^-1.Meanwhile,the metal halide perovskite materials have attracted more and more attention because of its high optical absorption coefficient,long carrier diffusion length and excellent carrier transport characteristics.In view of the problems of graphene single device,we compound graphene and Cs Pb I₃ perovskite quantum dots to form heterojunction,which not only makes up for the defect of low light absorption rate of graphene,but also makes full use of the carrier characteristics of perovskite material.In this paper,we first obtain large area graphene films with few layers on Si O₂/Si insulating substrate by plasma-enhanced chemical vapor deposition.Then we analyzed the layers of graphene by Raman spectrum and transmittance analysis.Meanwhile,the morphology and defects of graphene were characterized by SEM.On the basis of obtaining excellent few layer graphene,the field effect transistor based on large area graphene was further prepared by magnetron sputtering and mask method.Secondly,the photoelectric properties of graphene field effect transistor?GFET?are tested by Keithley 4200A semiconductor analyzer and visible laser source.In the test results,the ohmic contact behavior between graphene and electrode and the bipolar characteristics of graphene are proved.Furthermore,the photoelectric conversion characteristics of the device under different wavelengths of visible light are analyzed and discussed.The results show that the device can effectively achieve photoelectric conversion under the illumination of 405nm,515nm and 650nm,The excellent performance is achieved under the illumination of 405nm,its response is up to 250A·W^-1 and the photoconductive gain and detection rate are 3.9×10¹⁰,1.3×10¹¹ Jones,respectively.Finally,Cs Pb I₃ perovskite quantum dots were prepared and characterized.Then,perovskite quantum dot solution is coated between the channels by spin coating method on the basis of GFET,and graphene/perovskite quantum dot hybrid photodetector is obtained.Through the test and analysis,the results show that the device can effectively achieve photoelectric conversion under the illumination of 405nm,515nm and 650nm,which proved that the huybrid device has obvious optical response characteristics in the visible light band.Under the illumination of 405nm wavelength and 1.2?W intensity,the maximum photocurrent is 0.852m A,and the response rate and detection rate are 68 A·W^-1 and 9.6×10¹⁰ Jones.