| Organometal halide perovskite materials have been widely used because of their excellent optoelectronic properties.However,the migration and accumulation of ions or vacancies in the organometal halide perovskite materials under an external electric field can lead the device life and reliability decrease,which seriously hinder the practical process of the perovskite materials.In this thesis,MAPBX3(MA+=CH3NH3+,X=Cl-,Br-,I-)single crystals are chosen as the study object,and the effects of ions migration and accumulation near electrode regions are systematically studied.The regulations of ions migration and accumulation in the device are carried out by using additive and subtractive manufacturing technologies.The main contents of this thesis are as follows:1.The influences of the accumulation of anions and cations in MAPbCl3,MAPbBr3 and MAPbI3 single crystals on the related optical properties of the micro-regions near electrode were studied by micro spectral measurement system.The conclusions obtained from experiment were demonstrated as follows,Firstly,the accumulation of halide ions,methylamine ions and halide vacancies in the anode or cathode regions can lead to the increase or decrease of fluorescence intensity in the corresponding regions,accompanied by the red shift or blue shift of the fluorescence peak wavelength respectively,which were particularly obvious in MAPbI3 crystal.Secondly,the accumulation of halide ions and the corresponding halide vacancies will greatly affect the carriers recombination dynamics process.Thirdly,the accumulation of halide ions can cause frequency shift of the specific Raman spectrum vibration modes,demonstrating that the accumulation of ions will affect the interaction between the organic cation MA+and the inorganic Pb-X octahedral structure.The related results provided a certain of theoretical and experimental basises for the subsequent regulation of ions migration and accumulation.2.The metal-semiconductor-metal type photodetector was prepared on the(100)lattice plane of MAPbBr3 single crystal.At the same time,gold-perovskite heterostructures were introduced on the surface of the detector.Then the measurements of electrical parameters of the photodetector had been performed with or without heterostructures.The conclusions obtained from experiment were demonstrated as follows,Firstly,the ionic conductance of the detector with heterostructure was effectively suppressed and the detection of the device can maintain a certain of stability when the bias voltage increased,which proved that the heterostructures can regulate the ions migration and accumulation to a certain extent,and improve the stability of the device.Secondly,due to the localized-plasmon resonate effect in the metal structure,the light absorption of the detector was enhanced and the performance parameters such as photocurrent,responsivity and external quantum efficiency of the device were greatly improved under different powers and wavelengths of light irradiation(under the irradiation of 630 nm,0.5 mW laser and 5 V bias,the photocurrent increased by about 109%,responsivity and external quantum efficiency increased by about 84%).The regulation of ions migration and accumulation were initially realized through additive manufacturing technology,as well as improving device performance and maintaining device stability.3.The ionic conductance was measured along the[100]and[110]crystal directions of MAPbBr3 single crystal(100)lattice plane respectively.The results showed that the ionic conductance of[110]crystal direction was higher than that of[100]crystal direction.Based on the above results,the CNC mode of the 3D printing system was used to fabricate the surface microstructure along the[110]crystal direction.The micro-area fluorescence mapping was used to characterize the microstructure region polarized along the[100]crystal direction.The results showed that the fluorescence intensity in the contact area between anode and microstructure was increased.The fluorescence intensity in the contact area between cathode and microstructure was decreased.Combined with the above research results,it was proved that the ions had migrated and accumulated along the[110]direction.The fabrication of surface pattern structure initially realize the regulation of ions migration paths,accumulation distributions,and built-in electric field strengths,and achieve the purpose of improving device stability and work life. |
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