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We study the effect of Gaussian energetic disorder on the organic field-effect transistors (OFETs) with surprisingly high field-effect mobility and the low contact resistance. The numerical device simulation assumes the thermally assisted hopping transport and injection in disordered semiconductors. The results are analyzed with the power-law field-effect mobility and the asymptotic power-law contact resistance model. Transistor parameters extracted by the models reveal that a higher Gaussian disorder, which leads to a lower injection barrier and a larger mobility enhancement, is the origin of the high field-effect mobility and the low contact resistance. [ABSTRACT FROM AUTHOR]

We present a drain current model and a consistent parameter extraction method for organic field-effect transistors (OFETs) considering the gate voltage-dependent contact resistance and mobility by power-law. The physical origin of the asymptotic power-law dependence of contact resistance is elaborated based on the current crowding model. The parameters of a new model can be completely extracted without ambiguity by the proposed extraction method based on the linear fitting. Pentacene-based OFETs with the Au source/drain contact in a staggered configuration experimentally validate the proposed model and the extraction method, which further reveal the bulk resistivity as the major contribution to contact resistance. [ABSTRACT FROM AUTHOR]

Accurate description of the electrical behavior of organic solar cells (OSCs) becomes necessary with the advance of OSC technology toward up-scaled modules. We propose here a compact model for OSCs, by identifying different regimes present in the device operation in dark and under light: OFF, exponential sub- V\mathrm{\scriptscriptstyle ON} , power-law above- V\mathrm{\scriptscriptstyle ON} , and photocurrent. We also present a complete parameter extraction method for the model. In addition, we discuss the effect of the resistivity of transparent electrode and the device size on the OSC performance, by illustrating expected modifications on the current–voltage curve and parameter values. [ABSTRACT FROM PUBLISHER]

In spite of impressive improvements achieved for organic field-effect transistors (OFETs), there is still a lack of theoretical understanding of their behaviors. Furthermore, it is challenging to develop a universal model that would cover a huge variety of materials and device structures available for state-of-the-art OFETs. Nonetheless, currently there is a strong need for specific OFET compact models when device-to-system integration is an important issue. We briefly describe the most fundamental characters of organic semiconductors and OFETs, which set the bottom line dictating the requirement of an original model different from that of conventional inorganic devices. Along with an introduction to the principles of compact modeling for circuit simulation, a comparative analysis of the reported models is presented with an emphasis on their primary assumptions and applicability aspects. Critical points for advancing OFET compact models are discussed in consideration of the recent understanding of device physics. [ABSTRACT FROM PUBLISHER]

The quasi-static approach in the dynamic modeling considers that a thin-film transistor (TFT) reaches the steady-state instantaneously, and how to insert its behavior before steady-state is an important issue. In this paper, dynamic responses of silicon-based TFTs under gate-voltage pulse are studied in details. We experimentally distinguish quasi-static and non-quasi-static cases and we identify two charging regimes of the channel formation: channel propagation and charging of the fully propagated channel. We propose a model for the channel propagation, with a compact model-like approach to take into account the effect of defect states. [ABSTRACT FROM PUBLISHER]

We propose a theoretical description of the charge distribution and the contact resistance in coplanar organic field-effect transistors (OFETs). Based on the concept that the current in organic semiconductors is only carried by injected carriers from the electrodes, an analytical formulation for the charge distribution inside the organic layer was derived. We found that the contact resistance in coplanar OFETs arises from a sharp low-carrier-density zone at the source/channel edge because the gate-induced channel carrier density is orders of magnitude higher than the source carrier density. This image is totally different from the contact resistance in staggered OFETs, in which the contact resistance mainly originates from the resistance through the semiconductor bulk. The contact resistance was calculated through charge-distribution functions, and the model could explain the effect of the gate voltage and injection barrier on the contact resistance. Experimental data on pentacene OFETs were analyzed using the transmission-line method. We finally noticed that the gate-voltage-dependent mobility is a critical factor for proper understanding of the contact resistance in real devices. [ABSTRACT FROM AUTHOR]

Presents a study that introduced a method for optimal positioning of piezoelectric actuators and sensors on a flexible structure. Information on the modeling of piezoelectric actuators and sensors; State model of the plate with actuators and sensors; Energy-based approach for actuators and sensors and sensors positioning.

In this letter, decisive advantages of the staggered-type organic field-effect transistors (OFETs) over the coplanar type are elucidated by 2-D device simulation. It is found that the charge transport in the channel is not limited by the contact electrode in staggered OFETs, whereas coplanar OFETs show strongly contact-limited behavior. This dissimilarity originates from the continuity (staggered) or discontinuity (coplanar) of the carrier concentration at the channel ends, which is directly connected to the channel potential profile. The calculated current–voltage curves also support these arguments as the current in coplanar OFETs follows the contact-limited transistor model. [ABSTRACT FROM PUBLISHER]