A bio-inspired organic semiconductor 5,5 0-diphenylindigo shows excellent and well-balanced ambipolar transistor properties; its hole and electron mobilities are 0.56 and 0.95 cm 2 V À1 s À1 , respectively. The enhanced performance is attributed to the extended p-p overlap of the phenyl groups as well as the characteristic packing pattern that is a hybrid of the herringbone and brickwork structures. The ambipolar transistor characteristics are analyzed considering its operating regions, where a large unipolar saturated region appears due to the difference of the electron and hole threshold voltages. Scheme 1 Structures of indigo derivatives.

n-Channel organic transistors with excellent air stability are realized on the basis of charge-transfer complexes, (BTBT)(TCNQ), (BTBT)(F 2 TCNQ), (BSBS)(F 2 TCNQ), and (BTBT)(F 4 TCNQ), where BTBT is benzothieno[3,2b]benzothiophene, BSBS is benzoseleno[3,2-b]benzoselenophene, and F n TCNQ (n = 0, 2, and 4) are fluorinated 7,7,8,8-tetracyanoquinodimethanes. These complexes consist of mixed stacks of essentially neutral molecules, and the transistors are air stable even after several-month storage in ambient conditions.

International audienceA series of thin-film n-channel organic field-effect transistors based on various birhodanines, 3,3'-dialkyl-5,5'-bithiazolidinylidene-2,2'-dione-4,4'-dithiones (OS-R) and their sulfur analogues, 3,3'-dialkyl-5,5'-bithiazolidinylidene-2,4,2',4'-tetrathiones (SS-R) are studied. The SS-R compounds have tilted stacking crystal structures, whereas the OS-R compounds show basically herringbone structures. The alkyl chain R length and the intermolecular S-S interactions influence the molecular packing to realize excellent long-term air stability in the thin-film transistors

Meniscus, a curvature of droplet surface around solids, takes critical roles in solution-based thin-film processing. Extension of meniscus shape, and eventual uniform film growth, is strictly limited on highly lyophobic surfaces, although such surface should considerably improve switching characteristics. Here, we demonstrate a technique to control the solution meniscus, allowing to manufacture single-crystalline organic semiconductor (OSC) films on the highest lyophobic amorphous perfluoropolymer, Cytop. We used U-shaped metal film pattern produced on the Cytop surface, to initiate OSC film growth and to keep the meniscus extended on the Cytop surface. The growing edge of the OSC film helped maintain the meniscus extension, leading to a successive film growth. This technique facilitates extremely sharp switching transistors with a subthreshold swing of 63 mV dec−1 owing to the effective elimination of charge traps at the semiconductor/dielectric interface. The technique should expand the capability of print production of functional films and devices.