Research Of Transport Mechanism Of Organic Semiconductors And Electrical Properties Of The Device

The research of the optoelectronic and electrical transport properties in conjugated semiconducting polymers has drawn intensive attention because of their potential applications in organic semiconductor devices such as light-emitting diodes and field-effect transistors. However, the charge transport mechanism in organic semiconductor materials is not clear. Understanding their charge-carrier transport properties is very useful to improve the device performances, design and synthesize better materials.Alternating current(AC) impedance spectroscopy(IS) is powerful tools to investigate the charge transport and relaxation processes in solid state devices. In this paper, a semi-analytic expression of impedance spectroscopy is derived as the mobility being a function of temperature, carrier density and electric field, it can avoid many numerical calculations when we solve the impedance.The main work and results are listed as follows:(1) We introduced the development of organic semiconductors and organic semiconductors classification and several organic electronics in the first chapter. We introduced the carriers in organic semiconductors and the method measurement mobility and analyzes the factors affecting mobility. We made a detailed description of semiconductor carrier transport mechanism in third chapter. The last three chapters focus on research.(2) On the basis of carrier mobility model which proposed by Pasveer et al, a semi-analytic expression of impedance spectroscopy is derived, The formula is further extended to consider the trapped charges, series resistance to describe non-ideal contacts of polymer layers with electrodes, and parallel capacitance due to metallic electrodes.In order to verify correctness of semi-analytic expression, we apply it to the case with constant mobility, and compare the numerical results with exact solution. The figures show that the results calculated from semi-analytic expression almost are in completely agreement with the exact solution. This verifies that the semi-analytic expression is correct.(3) The numerical results are calculated and analyzed for two typical organic NRS-PPV and OC1C10-PPV diodes with parameters optimized by Pasveer et al. The extended formula is applied to MEH-PPV, BDMOS-PPV and AlQ3 devices; the numerical results are in good agreement with experimental data and support the Gaussian DOS of traps.