The Study Of Organic Field-Effect Transistors And The Circuit Simulation Model

Organic field-effect transistors(OFETs)are the transistors using organic semiconductive materials as active layers. In comparison with conventional inorganic transistors, OFETs have gained considerable interest due to their potential application in large-area, low-cost integrated circuits. Such applications include driving devices for active matrix flat panel displays, radio frequency identification tags, low-end memory cards, etc. Field-effect transistors based on such materials present several appealing features: they can be vacuum-deposited on large areas at room temperatures, they may be processed by spin coating and in the case of all-polymer systems, and they are suitable for the production of flexible integrated circuits. Although a lot of research groups focus on organic material synthesis, a self sustained electrical model for such devices is far from perfect right now. To understand the electronchemistry of organic materials and find the solution of stabilities of organic materials, a complete modeling and research on DC and AC is needed.In this paper, several theory models including the Small Polaron Model, the Multiple Trapping and Release Model and the Variable Range Hopping Theory, are introduced. And from the existing numerous organic theories of thin film transistors, one reasonable theory is chosen as the basis of our research, namely the Variable Range Hopping Theory. Then a mathematical model for the dc/dynamic current of organic thin-film transistors is proposed. This model is based on the Variable Range Hopping Transport Theory. A carrier may either hop over a small distance with a high activation energy or hop over a long distance with a low activation energy. And the mathematical expression of the current is formulated by means of the channel accumulation charge. It accurately accounts for below-threshold, linear, and saturation operating conditions via a single formulation, and does not require the explicit definition of the threshold and saturation voltages. The resulting mathematical expressions are simple and suitable for CAD applications. Then some parameters from the experimental data are distilled. Through repetitious tries, a group of parameters are obtained, which make a very good agreement between experimental data and the analytical model, with MATLAB software. It verifies the accuracy of the current expression of organic thin film transistor. Therefore the DC Simulation Model of organic thin film transistors is obtained.In order to search for a software which can be used to simulate the performance of the organic thin film transistor, this paper tried to explore the Level62 RPI TFT Model that is based on the Hspice software. This model is mainly directed against the Inorganic Thin Film Transistor Circuit Simulation Model. Here this paper distinguished the organic materials and inorganic materials, amended part of the model parameters. Through repetitious tries, a group of parameters that make a very good agreement between experimental data and the analytical model are obtained. Finally, several basic logic circuits designed by organic field-effect transistors are simulated by this model. And the result is perfectly ideal. All these results can prove that the model is correct and practical.