Ryonosuke Sato

Thermoelectric power of oriented thin-film organic conductors

The temperature dependence of thermoelectric power is investigated down to low temperatures for oriented thin films of organic conductors. In addition to the evaporated films, highly oriented films consisting of nanoparticles are fabricated by the solution method for tetrathiafulvalene:tetracyanoquinodimethane (TTF)(TCNQ) and (TTF)[Ni(dmit)2]2 (dmit: 1,3-dithiole-2-thione-4,5-dithiolato). The resulting films show n-type thermoelectric power, whose temperature dependence is similar to the single-crystal result along the most conducting axis. Owing to the ordered orientation and nanostructures, the thermoelectric power factor is considerably improved in comparison with the ordinary organic films.

Air-stable ambipolar organic transistors based on charge-transfer complexes containing dibenzopyrrolopyrrole

It has been known that organic charge-transfer complexes with a mix-stacked structure show transistor properties, and particularly complexes containing 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) show air-stable n-channel transistor properties in thin-film transistors, though ambipolar properties have been reported in a few single-crystal transistors. Here we report, when TCNQ is replaced by 2,5-dimethyl-N,N′-dicyano-p-quinonediimine (DMDCNQI), the dibenzopyrrolo[3,2-b]pyrrole (DBPP) complex exhibits ambipolar properties even in the thin-film transistor. The ambipolar operation is stable in air after several weeks. In addition, the transistor shows a very small difference in the electron and hole threshold voltages.

Air-stable n-channel organic field-effect transistors based on charge-transfer complexes including dimethoxybenzothienobenzothiophene and tetracyanoquinodimethane derivatives

A new donor molecule 3,8-dimethoxy-[1]benzothieno[3,2-b][1]benzothiophene (DMeO-BTBT) is synthesized and the charge-transfer complexes with fluorinated 7,7,8,8-tetracyanoquinodimethane (Fn-TCNQ; n = 0, 2, and 4) are prepared. All complexes (DMeO-BTBT)(Fn-TCNQ) have mixed stack structures, and the thin-film and single-crystal organic transistors show n-channel transistor performance both in vacuum and in air even after one-year storage. Although the performance and stability of the thin-film transistors are improved according to the acceptor ability of Fn-TCNQ, all single-crystal transistors exhibit similar performance and excellent air stability, among which the (DMeO-BTBT)(F2-TCNQ) transistor exhibits the highest mobility of 0.097 cm2 V−1 s−1.

CCDC 1409470: Experimental Crystal Structure Determination

Related Article: Toshiki Higashino, Masaki Dogishi, Tomofumi Kadoya, Ryonosuke Sato, Tadashi Kawamoto, Takehiko Mori|2016|J.Mater.Chem.C|4|5981|doi:10.1039/C6TC01532H