Design Of Graphene/CH₃NH₃PbI₃ Photodetector Structure And Research On Its Photodetection Performance

The methylamino lead halide(CH₃NH₃PbX₃)has a large light absorption coefficient,long carrier diffusion length,showing great potential in the light collector of photodetectors.At the same time,graphene,with fast response rate and ultra-high carrier mobility,can be used to composite with perovskite to enhance the carrier mobility and diffusion length of photogenerated electrons and holes in the perovskite.However,the presence of graphene is equivalent to introducing a leakage channel,resulting in a photodetector with a higher dark current and a low on/off current ratio.In order to solve this problem,a method of using probes to scribe secondary channels on graphene to reduce the resistivity of graphene and reduce dark current were proposed.At the same time,the horizontal‘graphene-perovskite(CH₃NH₃PbI₃)-graphene'Schottky structure were realized at the channel,which promoted the effective separation of photogenerated carriers.The design of this graphene-perovskite-graphene(GPG)structure photodetector with a secondary channel had successfully achieved the improvement of the photoelectric device performance.In this paper,a few-layer graphene film and a high-crystallinity CH₃NH₃PbI₃ film were prepared by chemical vapor deposition and one-step anti-solvent spin coating,respectively.The graphene and perovskite were characterized by optical microscope,scanning electron microscope,transmission electron microscope,Raman spectroscopy,X-ray diffractometer,ultraviolet spectrophotometer and photoluminescence spectrometer.The graphene morphology,number of layers,light transmittance and other information as well as the light absorption capacity,carrier lifetime and phase composition of the CH₃NH₃PbI₃ film were obtained.Secondly,the structure design and mechanism analysis of the perovskite/graphene composite photodetector were carried out.A probe was used to scribe the secondary channel on the graphene and then the CH₃NH₃PbI₃ film was spin-coated on the graphene.In the middle of the channel,CH₃NH₃PbI₃ contacted both sides of the graphene to form a horizontal‘graphene-perovskite-graphene'Schottky junction.And the upper CH₃NH₃PbI₃and the lower graphene form a vertical‘graphene-perovskite'Schottky junction.This article analyzed the mechanism of the two Schottky junctions.Finally,the performance of GPG photodetector device was tested,and the spectral response characteristics and optical power response characteristics of the GPG photodetector were investigated.Then,the influence of the thickness of CH₃NH₃PbI₃ film and the number of channels on the performance of the photodetector was studied.Studies have shown that GPG photodetectors have high switching ratio and stability.Under the irradiation of 452 nm laser(the optical power intensity is 1.83 m W/cm²),the value of photocurrent is 6.60?A,and the response rate is 24.04 m A/W.The corresponding switching ratio and detection rate are 2.64×10³ and 3.55×10⁹ Jones,respectively.Subsequently,the device was applied to a flexible substrate,under the condition of a bending angle of 30°,100 bending times and a long-term test(10 min),the photocurrent of the flexible device basically maintained 90%of the original performance.It is proved that the device has good bending resistance and has a wide range of application prospects in the field of flexibility.