We have investigated the characteristics of bottom-gate and top-contact type field effect transistors fabricated with polycrystalline thin films of a liquid-crystalline organic semiconductor, 2-decyl-7-phenyl-benzothienobenzothiophene (Ph-BTBT-10), with a p-type dopant, tetrafluoro-tetracyano-quinodimethane (F4-TCNQ). We found that the contact resistance between the semiconductor and electrode was reduced from 3.0 kΩ cm to 1.2 kΩ cm by contact doping with F4-TCNQ, and to 0.9 kΩcm by subsequent thermal annealing of the films, in which the F4-TCNQ dopant diffused from the surface to the interior of the Ph-BTBT-10 thin film. In addition, we found that contact-doped and thermally annealed devices showed higher mobility and smaller threshold voltage in short-channel devices compared to pristine devices. We conclude that thermal diffusion of dopants to improve FET performance is an important technique.

Orientational control within thin films is crucial for the preparation of organic field effect transistors (OFETs). The highly ordered liquid crystalline smectic E phase (SmE) is known as a powerful...

We have proposed a new fabrication process of donor and acceptor charge transfer complex thin films using thermal diffusion. 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ) were vacuum-deposited on 2,7-didecylbenzothienobenzothiophene (C10-BTBT) thin films fabricated by spin-coating, and F4-TCNQ molecules were diffused into C10-BTBT thin films by thermally annealing. The X-ray diffraction pattern and field effect transistor of thermally annealed thin films indicated the crystal structure of the charge transfer complex of C10-BTBT and F4-TCNQ and n-channel operation in air, respectively. We conclude that it is good process to use the thermal diffusion for the fabrication of the large area thin films of charge transfer complex.

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