Magnetoresistance Effect Of Disordered Organic Semiconductors

Organic semiconductors have attracted extensive research and attention due to their advantages of easy processing and low cost.With the deepening of the research,researchers found the magnetoresistance effect of organic semiconductors(OMAR),and believed that better organic semiconductor devices could be developed and improved by studying the magnetoresistance effect.Researchers have revealed that both carriers and mobility can be affected by magnetic field.The research on magnetoresistance effect of organic semiconductors is of great significance for the development,utilization and improvement of devices,which makes researchers want to uncover the mystery of organic magnetoresistance effect.However,the effect of organic magnetoresistance should be very complex,and there is no complete conclusion in the world at present.This paper is only for one of the research.In the first chapter,the research background of organic magnetoresistance effect is reviewed,including organic semiconductors,magnetoresistance effect and the research progress of impedance spectroscopy.In addition,the research status of magnetoresistance effect at home and abroad is also introduced.Finally,the research significance of organic magnetoresistance effect is described.The second chapter mainly introduces the related theories of organic semiconductor magnetoresistance effect,introduces two types of magnetoresistance effect and three kinds of magnetoresistance effect models that researchers are familiar with,and finally lists two common carrier mobility models,which lays a foundation for the subsequent derivation of organic magnetoresistance effect model and impedance spectroscopy(IS)research.In the third chapter,a series of theoretical derivation of the organic magnetoresistance model is carried out on the basis of previous studies,and some improvements are made on the basis of previous studies on the magnetoresistance effect model.In the literature,Boltzmann statistics is used,and the effective density of States is regarded as a constant.In this paper,Fermi statistics is used,and the relationship between temperature is considered,Therefore,the model used in this paper is more reasonable than that in the literature,and a simple theoretical basis is constructed.The mobility,an important factor in the magnetoresistance effect,is also theoretically deduced.At the same time,the impedance spectrum is also an important way to study the related effects of organic semiconductors,so this paper deduces the corresponding formula for the impedance spectrum of organic semiconductors,and uses the Poole-Frenkel model?(T,E)and Pasveer mobility model ?(T,p,E)to study the impedance spectrum of organic diodes,the relationship between direct current and voltage,and obtains a judgment on the mobility model.In the first part of the fourth chapter,we use the formula and model to write the basic program of Matlab,collect the experimental data at different temperatures,compare with the theoretical model,optimize the parameters in the mobility model,and get the best agreement between the theoretical and experimental results at t=200K,so we only discuss the trend of magnetoresistance effect with several important parameters at t=200K;In the second part,we compare the two mobility models and get the related properties of impedance spectrum and capacitance spectrum of organic diodes.In the fifth chapter,the work of this paper is summarized and analyzed,and the expectation and Prospect of the follow-up research on the magnetoresistance effect of organic semiconductors are put forward.