Fabrication And Characterization Of Photodetector Based On CH₃NH₃PbI₃/graphene Nanowall

In recent years,optoelectronic devices based on two-dimensional nano-materials,such as graphene has drawn a lot of attention.Because of their unique electrical and optical properties,Meanwhile,the organic-inorganic halide perovskites have attracted broad attention in the photoelectric devices.This perovskite materials CH3NH3 Pb I3 are extensively studied due to their high absorption coefficient,long charge carrier diffusion length and excellent mobility.However,owing to its zero band gap and low light absorption,pure graphene has been limited in many high performance photoelectronic applications.In order to extend application of graphene,combining graphene with other materials is a good solution.This dissertation is aiming to achieve high performance graphene electrophotonics by combining with vertical-oriented graphene nanowalls and organic halide perovskite.First,we used oxygen plasma to etch graphene grown on the back of copper foil;Then,etching solution(HCl:H2O2:H2O = 2:1:40)was used to effectively remove copper foil substrate;Finally,ammonia solution was introduced to neutralize p-doping of graphene from residual acid etchant.Using the shift craft optimized it can lead the CVD graphene film to transfer to the goal substrate perfectly,and the film transferred is clean and non-damaged.by comparison to the traditional PMMA aqueous method shift,the Dirac point of GNRFET is obviously reduced(reducing the p dping),and the mobility is remarkably enhanced(reducing the impurity scattering).Optimizing the key process of graphene photodetector fabrication.we introduced an interlayer(PMMA)between the photoresist and graphene,and efficiently eliminated the polymer residue after patterning the graphene.We also adopted several kinds of methods(such as reducing the concentration of PMMA in the graphene transfer process?etching solution?and ammonia solution immersion etc.)to reduce the p-type doping of graphene which can obtain high carrier(electrons or holes)mobility.The optoelectric properties of devices were tested and analyzed,which exhibited ohmic contact behavior and bipolar characteristic of graphene.A perovskite/GNWs hybrid photodetector was fabricated.a high-performance methylammonium lead iodide perovskite-carbon nanowall hybrid channel photodetector was fabricated by using the method of radio frequency plasma enhanced chemical vapor deposition(RF-PECVD).It has been shown that the presence of PbI2 species in the GBs upon thermal annealing lead to a successful passivation that control the carrier behavior along the heterojunctions.leding to improved carrier behavior possibly due to reduced recombination in the GBs and the perovskite/GNWs surface.Then perovskite/GNWs hybrid photodetector not only possess a high performance but also have a stable performance,were tested and analyzed,and the high performance is due to the synergistic function of hopping-like effect.The hybrid photodetectors obtain a high responsivity of 3.2 x 105 A/W and a fast response speed of 8 ms at rise time and 24 ms at delay time.