Organic Semiconductor Einstein Relationship Between Research And Its Applications

Organic semiconductors are seen as insulating materials typically for a long time, until scientist synthesized conducting polymer in 1970s, and theoretical research of organic semiconductors is lagged. Recently, conjugated semiconducting polymers are investigated intensively for their application in areas as light-emitting diodes, photovoltaic cells, and transistors. The application of organic semiconductors and device is faster than before. As the most popular semiconductors, organic electro-luminescence materials have prompted development of organic semiconductor devices. Improving photoelectric properties of device is still pursuing destination of people. Researchers have introduced ETL and HTL, adopted multiple-course construction in the electro-luminescence devices, which will be helpful to balance injection of electrons and holes, and can improve the mobility, stability, degree of order and efficiency.Researching electro-luminescence materials theoretically is a very important and valuable subject. The physical processes of electro-luminescence include injection,migration of carriers,creation of exciton and emission of photons. People usually use Monte Carlo simulations to research these processes, or obtain numerical under some simplified conditions, and learn from the theory of inorganic semiconductors. Although many theoretical models can give reasonable explanations to different experimental results, it has not been determined that which model is in more agreement with practical situation.The generalized Einstein relation (GER) relates the diffusion coefficient D with the mobility of charge carriersμ, and is very important. In the past several years, people found that the GER is dependent with Fermi energy, concentration of carriers and concentration of doped affect the D/μ, and gives non-traditional values. In this work, we propose the dependence of the GERin disordered organic semiconductors, with electric field, chemical potential and charge concentration. We also calculated and discussed the GER as considering the electric field dependence for two p-type polymers. The main results are listed as follows:(1). We put forward and analyzed dependence of the GER with charge concentration, chemical potential of p-type organic semiconductors based on the research of Yohai Roichman. The traditional form of GER should be replaced by the new form.(2). Organic semiconductors are non-equilibrium under an electric field, the Fermi energy should increase as the electric potential exists for holes. We should take the electric potential into account and introduce the potential-dependent GER(PDGER ) in disordered organic semiconductors.(3). We calculated and analyzed electric characters of two polymers layers of NRS-PPV and OC1C10-PPV based on thePDGER . The results exhibit some different physical property as compared with the traditionalGER, and maybe are instructive to future theoretical and experimental researches.