Study Of Charge Carrier Transport In Organic Semiconductor Thin-film Devices

In recent years, the study of organic solid electric devices has attracted much interest and obtained great achievements. At present, the devices with good stability, long lifetime, low applied voltage is required. Comparing with the great achievement of experiment, the physical theory of the electric carrier transport in organic solid electric devices is insufficient, which greatly restricts to improve the performance of the organic solid electric devices. Because the carrier transport in inorganic semiconductor is different from in organic semiconductor, it is greatly needed to build a theory model holding for organic semiconductor. Based on those problems, following work has been done.1. For single layer organic film devices, with ohmic injection, the analytical relationship between current density and applied voltage has been derived for trap free organic film. The relationship between current and film thickness, the relationship between current and relative trap depth have been studied by using numerical method. At same time, the distribution of potential, electric field, carrier density in the bulk of organic film have been researched when with traps in organic film, a new criterion to judge the current conduction state also has been obtained. For ambipolar single layer organic film devices, the relationship between applied voltage and current density is given out to explain the reason why the current in ambipolar single layer organic film devices is larger than in monopole single layer organic film devices.2. The carrier injection models at the interface between electrode and organic film are reviewed, and a new theory model is developed to explain the hole inject from ITO anode into organic semiconductor G1-para-Ir(ppy)₃.3. By taking the injection limited (IL) and bulk limited (BL)current into consideration at the same time, for devices with non-ohmic injection contact and low-field operation, the temperature influence on the device's J-V characteristic, the carrier density and the filed distribution in the organic layer were studied by using numerical method.4. For the double layer organic thin-film devices, the dependences of the optimal thickness ratio on the characteristic trap energy, total trap density and mobility were calculated and analysised. For the carrier transport at 00 interface, on the basis of the Miller-Abrahams formalism, an analytical model for charge transport has been developed.5. Analytical expressions of generalized Einstein relation for electron and hole transport in pure, physically doped and chemically doped organic semiconductor thin films have been developed.