Recombination Dynamics Diagnosis Of Photon-Generated Carrier By Microwave Dielectric Method

Microwave dielectric spectroscopy is a measurement technique based on the interaction of microwave and materials.The measurement technology has the advantages of non-contact measurement,fast signal acquisition speed and high measurement time resolution.Therefore,the microwave dielectric spectroscopy has a good application prospect in the field of recombination dynamics diagnosis of photon-generated carrier of photoelectron functional materials.In this paper,based on the principle of microwave dielectric spectroscopy of semiconductor photon-generated carrier recombination,a microwave dielectric spectroscopy system is built,which includes the selection of relevant microwave devices and the testing of microwave dielectric spectroscopy system.In the microwave device selection,the microwave resonant cavity is the core component of the microwave dielectric spectroscopy measurement system.In this paper,High Frequency Structure Simulator?HFSS?software is used to simulate the electromagnetic field distribution in microwave resonator.The simulation results show that the simulation results are in agreement with the theoretical values.In the TE103 resonant mode,the simulation results show that the strongest electric field is located at the center of the resonator and the results as a basis for the cavity wall of the resonator.In the nanosecond pulse?pulse width 5-7 ns?excitation conditions,the time resolution of the microwave dielectric spectroscopy system can reach 15 ns?Gaussian instrument response function,half full width?,in the femtosecond pulse?pulse width less than 100 fs?excitation conditions,the system measurement time resolution can reach 1-2 ns.Organometal halide perovskite?CH₃NH₃PbX₃,X-Cl,Br,I?,as a new photovoltaic material,is the focus of solar cell research.The study of photon-generated carrier recombination kinetics of perovskite thin films can provide a strong scientific basis for the design and production of perovskite solar cells.In this paper,the photon-generated carrier recombination kinetics of organometal halide perovskite thin films is studied by using a microwave dielectric spectroscopy system and main work are mainly divided into three parts:?1?In this paper,the influence of the incorporation of Cl on the photophysical properties of perovskite films is described from the perspective of photon-generated carrier recombination using microwave dielectric spectroscopy.The experimental results show that the free carrier recombination life of CH₃NH₃PbI_3-xCl_x perovskite film increases from 67 ns to 157 ns compared to CH₃NH₃PbI₃ perovskite thin film,and the shallow bound level?5-30 me V of binding level?carrier recombination life increased from 290 ns to 492 ns.In addition,by comparing the photogenerated recombination kinetics of CH₃NH₃PbI₃ and CH₃NH₃PbI_3-xCl_x perovskite films,it was found that the heat activation process of the shallow strained level carriers had a more significant effect on the carrier recombination kinetics.It can be inferred that the doping of Cl elements introduces more shallowly bound states in the films,while reducing the density of deep bound states.?2?In this paper,the photon-generated carrier recombination of CH₃NH₃PbBr₃ perovskite films was measured in resonant excitation mode and nonresonant excitation mode.The experimental results show that the photogenerated recombination process is divided into a fast decay stage and a slow decay stage.When the free carrier concentration is reduced to a certain extent,the free carrier reaches the heat balance with the shallow straining level?the binding level depth 5-30 me V?carrier.In particular,in the resonant excitation mode?558 nm?,the time for the carrier to reach heat balance at the free carrier and shallow level carrier is about 56 ns.Under non-resonant excitation?355 nm?,the time for the carrier reach heat balance is longer,about 848 ns.?3?The change of photon-generated carrier recombination dynamics of CH₃NH₃PbI₃ perovskite thin films after the lighting-darking is also studied in this paper.The experimental results show that the photon-generated carrier yield of the perovskite film increases obviously after the light soaking-darking,and the photon-generated carrier yield decreases rapidly with the re-treatment of the light soaking.