In addition, a potential method is developed to calculate the source-drain current and study the relaxation process using the electrical characteristics. The proposed model illustrates the physical origin of a change in the activation energy through its simplicity and analytic nature. Such a physical model can be applied to describe the experimental relation among thermally activated physical quantities such as the conductance and the mobility in organic semiconductors. In particular, a physical model relevant to the activation energy in the organic transistors is proposed.
The purpose of the present article is to shed some light on the devices physics of electron transport in the organic transistors by virtue of the energy and momentum conservation equations. One drawback of the Meyer-Neldel relation is that it is a phenomenological model and some of its parameters lose their underlying physics, although its results are consistent with experiments. Accurate modeling of thermally activated physical quantities is usually difficult because there exists large variation in the experimental data.
The activation energy is a common factor in models 8. The physical meanings of the parameters in the Meyer-Neldel relation are unclear so far because it is a phenomenological model and the charge transport mechanisms are not fully understood yet 8, 11. Thermal activated physical quantities such as the conductance and the mobility in organic semiconductor devices obey an empirical relation, called as the Meyer-Neldel relation 8, 9, 10, 11. Experiments showed that the carrier mobility depends on the temperature and the gate voltage 8, 9, 10, 11. The field dependent mobility is thermally activated with the activation energy in an organic semiconductor device. Most of existing organic semiconductors are p-channel materials and only a small fraction of them are n-channel materials 7. But high mobility organic semiconductors may not be always valuable, for example, in the fabrication of the organic circuits that are applied to low-end devices 7. Most effort for improving the charge-carrier mobility has been done by optimizing current materials and developing new materials. Understanding of the fundamental physics of organic semiconductor devices such as light-emitting diodes (OLEDs), field-effect transistors (OFETs) and solar cells, accurate modeling of charge transport in these devices is prerequisites to optimize their performances and design organic circuits to realize flexible electronics. In recent years organic semiconductors have gained considerable interest in order to develop low-cost and large-area integrated flexible circuits 1, 2, 3, 4, 5, 6.
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