Model for the injection of charge through the contacts of organic transistors

Abstract

A compact model has been employed in organic thin film transistors (OTFTs) to study the electrical characteristics of the contacts, which are formed between the organic layer and source/drain electrodes of the OTFT. The model shows the importance of interrelating different physical phenomena: charge injection, redox reactions at the interface, and charge drift in the organic semiconductor. The model reproduces and explains several features that have been reported for current-voltage curves, ID-VC, at the contacts of OTFTs. The ID-VC curves are extracted from the experimental output characteristics by two techniques. One technique uses a set of transistors with different channel lengths and a simultaneous extraction of the ID-VC curve and the mobility of carriers in the channel of the transistor. When a set of transistors with different channel lengths is not available, we propose an iterative method for the simultaneous extraction of the ID-VC curve and the mobility by changing the gate bias voltages.

Versatile model for the contact region of organic thin-film transistors

“…The physical origin of model (3) lies behind the solution of the transport equations in a metal-organic structure, which provides the following relation between the current density j and the applied voltage V C [28,29,55,56]:…”

“…Overall, transistor models must be consistent with the underlying physics. In particular, the contact models must be adapted to different physical mechanisms that limit the charge injection through a metal-organic structure, such as space-charge limited conduction, thermionic emission and the Fowler-Nordheim tunneling [28,29], or even change the properties of the contact region such as light [30,31]. A generic analytical model and associated parameter extraction method for the current-voltage characteristics of OTFTs was derived in [19,20], which allows a functional model of the carrier injection through the source contact.…”

Compact Modeling of Organic Thin-Film Transistors with Solution Processed Octadecyl Substituted Tetrabenzotriazaporphyrin as an Active Layer

“…These expressions are theoretically justified by a previously proposed model that considers injection and transport of charge in organic diodes [19], [27], [28], [29]. In the cases analyzed in Figure 2 …”

“…Nevertheless, significant efforts have been spent in recent years to include the charge transport in organic semiconductor, which is clearly different from the transport in crystalline semiconductors, and is usually modeled with a gate-voltage dependent mobility [11], [12], [13], [14], [15]. They can also include detrimental effects produced by the contact region of the organic transistors [16], [17], [18], [19]. These models are also associated with methods to extract their respective parameters from the output characteristics of a transistor.…”

Evolutionary Computation for Parameter Extraction of Organic Thin-Film Transistors Using Newly Synthesized Liquid Crystalline Nickel Phthalocyanine

“…The solution of the transport equations in a metal-organic structure lies underneath the analytical Equation (6). In a metal-organic structure, the current density j and the applied voltage VC are related as [58,59,60,61]:leftleftVC=(23)[2jϵμθ]1/2[false(xc+xpfalse)3/2−false(xpfalse)3/2]leftxp≡jϵθ2μfalse[θqp(0)false]2; j=ID/S, where qp(0) is the charge density at the metal–organic interface, θ is the ratio of free to total charge density, qθp is the free charge density, S is the cross section of the channel where the drain current …”