Toshifumi Katagiri

Improved Field-Effect Transistor Characteristics of an n-Type Semiconducting Thiophene/Phenylene Co-Oligomer

We studied the organic field-effect transistor (OFET) characteristics of n-type thiophene/phenylene co-oligomers chosen as an organic semiconductor layer. The n-type characteristics were achieved by introducing trifluoromethyl groups on either molecular terminal. With crystals of this material, we fabricated OFET devices for which an MgAg alloy was used for drain and source electrodes and polymer layers were used as a gate insulator. In particular, the device fabricated on a poly(vinyl phenol) gate insulator layer shows a high electron mobility of 1.5 cm2 V-1 s-1. That on a poly(methyl methacrylate) layer indicates a low threshold voltage of 4.1 V. The polymer gate insulators and the low work-function metal play an important role in achieving a good device performance.

Development and Electronic and Photonic Characteristics of Thiophene/Phenylene Co-Oligomers

A novel class of organic semiconducting materials, thiophene/phenylene co-oligomers (TPCO), has been developed and synthesized. The materials are formed into crystals of high quality in a gas or liquid phase. These crystals exhibit unique optoelectronic properties such as a high carrier mobility and high quantum yield of emission. The transport properties have been studied on a device configuration of the field-effect transistor. The laser oscillation has definitively been observed for single crystals of the TPCO materials. In this article these optoelectronic features are presented and summarized.