Single-Crystal Growth and Charge Transport Properties of an Alternating Co-Oligomer Composed of Thiophene and Phenylene Rings

Abstract

We grow single crystals of a thiophene/phenylene co-oligomer (TPCO) composed of seven alternating thiophene and phenylene rings (AC'7). These crystals are grown in a liquid phase directly onto silicon substrates covered with a silicon dioxide layer. The grown crystals are well-defined hexagons and are composed of a molecular layered structure along the molecular length. Top-contact field-effect transistors are fabricated by depositing metal electrodes on the AC'7 crystals grown on the substrates. We estimate the field effect mobilities in the transistor device configurations. The mobility data are associated with the crystallographic results of the material. The devices produce a maximum mobility of ∼0.1 cm2·V-1·s-1. This value is higher than that obtained for another TPCO composed of five alternating rings (AC5). The present results indicate that AC'7 crystals are potentially useful for electrical device applications.

Refractive Index Measurements of Well-Defined Polygon Crystals of Thiophene/Phenylene Co-Oligomers

“…Figure 7 includes the related computational data of AC 0 7, BP1T, and AC5 as well. 18,31,32) With these three crystals the refractive indices are relevant to the ?ab-plane direction because of their monoclinic nature. 18,31,32) The corresponding refractive indices experimentally determined can be seen elsewhere.…”

“…10) To compare the results of BP2T and BP2T-OMe with those of other TPCOs, 14) we calculated the dispersions of 2,5-bis(4-biphenylyl)thiophene (BP1T), 16) 1,4-bis(5-phenylthiophen-2-yl)benzene (AC5), 16) and 2,5-bis[4-(5 0 -phenylthiophen-2 0 -yl)phenyl]thiophene (AC 0 7) 30) borrowing their atomic coordinates in the crystal as well. 18,31,32) The calculations were carried out from 480 to 700 nm for BP1T, from 500 to 750 nm for AC5, and from 540 to 800 nm for AC 0 7. Figure 3 shows micrographs of a well-defined hexagon BP2T-OMe crystal of $0:1 mm in size and a parallelogram BP2T crystal of $0:2 mm in size.…”

Exotic Optoelectronic Properties of Organic Semiconductors with Super-Controlled Nanoscale Sizes and Molecular Shapes

“…The said tilting angles of them are very small. [16][17][18][19] Here we define the TPCO molecular long axis as a line connecting terminal carbon atoms of the molecule. In the case of phenyl (thiophene) terminals, the relevant carbon atoms are located at the p-position on phenyls ( -position of thiophenes).…”

“…In the case of phenyl (thiophene) terminals, the relevant carbon atoms are located at the p-position on phenyls ( -position of thiophenes). [16][17][18][19] If the compound is modified with a substituent, the molecular long axis is represented by a line connecting a major substituent atom (e.g., an oxygen atom of the methoxy group, a carbon atom of the trifluoromethyl group, etc. ; see Fig.…”

“…These non-straight molecules produce peculiar crystallographic structures where the molecular long axes stand nearly upright against the bottom crystal face. [16][17][18][19] These structures are responsible for interesting electronic and photonic characteristics of the TPCOs. A high carrier mobility and unique emission characteristics can be counted among them.…”