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Joule's law opens a straightforward way to explore the operating mechanism of organic field-effect transistors, from the angle of inner transported heating. The microscopic dissipated power is calculated from the local conductivity and electric field, which solves the widespread difficulties in building a macroscopic model to determine the contact resistance. The result quantitatively discloses the correlation between the contact resistance and the charge transport properties covering energetic disorder, band-like and hopping transport as well as carrier mobility anisotropy. It turns out that in a staggered configuration with ideal Ohmic contact, the contact resistance is highly affected by the charge transport. [ABSTRACT FROM AUTHOR]

Abstract: A study of the contact resistance (R sd) in pentacene-based double-gate transistors is presented. In top-contact transistors, as the negative bias of the additional top-gate bias is increased, R sd decreases by over five orders of magnitude for small bottom-gate voltages. In bottom-contact transistors, R sd is reduced by about ten times for all bias values, implying improved charge transport in all operating regimes. The different tunability of R sd in top/bottom-contact transistors is attributed to different charge injection modulation by the coplanar/staggered top gate. Therefore, double-gate architecture offers a novel and effective approach to limit R sd and its relevant impacts on organic transistor. [Copyright &y& Elsevier]

We describe the mechanism of contact resistance reduction and improvement in device performance of organic field-effect transistors by chemical doping at the contact interface. Insertion of iron(III)trichloride into the contact interface significantly reduced the contact resistance from 200 to 8.8 kΩ cm at a gate voltage of -40 V, and a field-effect mobility of 7.0 cm2/V s was achieved in devices based on dioctylbenzothienobenzothiophene. The improved charge injection is attributable to a reduction in the depletion layer thickness at the contact interface and occupation of trap states in the access region due to the generation of charge carriers by contact doping. [ABSTRACT FROM AUTHOR]

The enhancement of the charge injection process by the insertion of an ultrathin (∼1 nm) contact oxide interlayer (COI) at the metal/organic material interface in organic field effect transistors (OFETs) is reported. Six different oxides were used as COI, and Al2O3 was found to exhibit the highest OFET mobility with a reduction in the average contact resistance (Rc) from 19.9 to 1.9 kΩ·cm. Photoelectron yield spectroscopy analysis revealed that the insertion of COI increases the work function of an Au contact and reduces the charge injection barrier at the interface, which lowers Rc and, therefore, results in enhanced device performance. [ABSTRACT FROM AUTHOR]