Research Programs

  1. Development of high-performance organic devices and their matrix arrays
  2. Synthetic chemistry to develop high-performance organic semiconductors
  3. Fundamental charge transport mechanisms in high-mobility organic semiconductors
  4. Interfaces of organic hetero-junctions: development and functions of their two-dimensional electronic states

3. Fundamental charge transport mechanisms in high-mobility organic semiconductors

Studies on fundamental charge transport using organic single crystals

organic SC transistorOrganic single crystals are such material that molecules are arranged in macroscopic scale in perfect periodicity. Developing the method of fabricating transistor structures with the organic single crystals, we opened the way to study intrinsic charge transport free from parasitic effects from grain boundaries. The class of the devices leads us solid and basic ideas to develop further high-performance devices with proper and fast evaluation of newly developed materials. It also provides us with a powerful tool to realize the best-performing organic transistors without scattering at grain boundaries.

The mechanism of charge carrier transport in organic semiconductors

hall effect measurementOrganic semiconductors in which electronic states in each molecule is only coupled by weak van-der Walls force, so that the mechanism of charge carrier transport through the series of the molecules is mysterious. We attack this question developing the method of measuring Hall coefficient precisely to directly extract coherence of the fundamental electronic state. It turned out that band-transport is successfully realized in such high-mobility compounds as rubrene, providing a positive idea for developing new materials with even higher performances.