The Concept of “Threshold Voltage” in Organic Field-Effect Transistors

Abstract

The photorefractive (PR) effect involves a photoinduced change of the refractive index in an optically nonlinear and photoconducting material. [1] This effect arises when photocharges, generated by spatially modulated light intensity, migrate through drift and/or diffusion processes and become trapped to produce a non-uniform charge density distribution. This charge separation then creates an internal space-charge field, which modulates the refractive index of the material through the linear electro-optic (EO) effect, also known as Pockels effect. The refractive index grating

Solution‐Processable Septithiophene Monolayer Transistor

“…In an organic thin film field effect transistor (OFET), transport of carriers in the channel between the source and drain electrodes occurs in the first layers of the semiconductor, close to the dielectric layer adjacent to the gate electrode. [2,3] Thus, the transport property in such a device is very sensitive to mole cular packing to the same extent as the interfacial interactions between the three electrode terminals. Down scaling the semiconducting film to a monolayer reduces the electrical transport to two dimensions.…”

Restraints in low dimensional organic semiconductor devices at high current densities

“…increasing the current density within the accumulation layer, but still within the linear regime of device operation according to the OFET model [1], a strong pronounced peak starts to appear at the source electrode. These conditions correspond to high gate bias, with a pronounced decrease in both the transconductance and µ f e,lin , where the assumption of a linearly distributed charge carrier density along the full transistor channel is violated.…”

“…These geometrical values lead to typical W/L ratios of about 80 and a low value of 0.42, for thin-film and single-crystal devices, respectively. The field-effect mobility in both the linear and saturation regime was extracted using the methodology proposed by Horowitz et al [1] and commonly used for OFETs. For TF1 a linear field-effect mobility of about µ f e,lin = 0.026 ± 0.001 cm 2 /Vs was calculated (inset Fig.…”

“…However, from a fundamental point of view, there are still many aspects related to the transport mechanisms and to the device parameters that need to be further understood since they play a crucial role in the final device performance. Typically, to describe the current-voltage characteristics of an OFET and to extract the field-effect mobility (µ f e ), the model developed by Horowitz et al is employed [1]. However, in this model it is usually assumed that the µ f e is constant, when it is known that in real OFETs gate bias (V G ) dependent mobility is commonly found [2,3].…”

Experimental study and analytical modeling of the channel length influence on the electrical characteristics of small-molecule thin-film transistors

“…For a good understanding of the transport properties of charge carriers in OTFTs, many of models have been introduced and developed. Furthermore, the modeling of OTFTs has left its infancy and has reached a level whereby a good agreement is reached with the experimental characteristics [26,27,[30][31][32].…”