The 2007 Laureates / Advanced Technology Category / Materials Science and Engineering

"Pioneering and Fundamental Contributions to Organic Molecular Electronics"
Dr. Hiroo Inokuchi initiated pioneering research on electrical conduction between molecules with benzene rings and established the scientific foundation for studying the electrical conductivity of organic materials. Further, he systematically elucidated an electronic structure of a wide variety of organic materials by photoelectron spectroscopy. Through a series of such studies, he established the academic base essential for studying the electronic properties, making fundamental contributions to the subsequent development of organic molecular electronics.

Chemist Who Made Pioneering Contributions to Development of Organic Molecular Electronics

Dr. Hiroo Inokuchi focused his attention on organic molecules with benzene rings*1 and initiated pioneering research on electrical conduction between such molecules, demonstrating that they could serve as useful materials for electronic components. This basic research played an essential role for the development of organic electronics, and has found application in a wide range of products, including mobile terminals and flat screen TVs.

The electronics industry has seen tremendous growth in the half-century since World War II. Specifically, the organic electroluminescent (EL) panel, characterized by high definition and thinness, has recently been attracting considerable attention as the next-generation display that will replace LCDs. Since late 1940's, Dr. Hiroo Inokuchi focused his attention on organic molecules having benzene rings and carried out pioneering research on electrical conduction between molecules. He further elucidated the electronic structures of organic compounds, and his findings played a critical role in the design and creation of EL devices in later years.

In the late 1940's, Dr. Inokuchi investigated the electrical resistance of pulverized carbon powders in a university laboratory in a constrained environment that cannot even be imagined today. In those days, it was common sense that organic materials were insulators that would not pass an electric current. However, Dr. Inokuchi, focusing on the fact that the structure of an organic molecule called violanthrone*2 has similarities to that of hexagonal basal plane of pure carbon, carried out various experiments under different conditions using ingenious measurement equipment. He played a leading role in the world's first discovery of semiconductive properties in organic materials. He later named organic materials with such properties 'organic semiconductors', and promoted the importance of this concept. He also played a major part in the discovery that the addition of bromine or iodine to an organic material such as perylene*3 causes a significant increase in electrical conductivity.

In 1975, Dr. Inokuchi helped to establish the Institute for Molecular Science (Okazaki, Aichi, Japan), which later became a world-class center for research on the electrical properties of molecules. Since then, he has made substantial contributions to the development of outstanding researchers and research groups and international academic interactions in his years of professorships and directorships.

While the technology of organic semiconductors has been evolving rapidly in recent years, the results of Dr. Inokuchi's discoveries are being applied to EL panels and other products that are in the process of commercialization. Furthermore, taking advantage of their better workability and deformation properties, and the lower density characteristic of organic materials, practical application of organic semiconductors has begun in mobile devices like cell phones for which miniaturization is required. Progress based on organic semiconductors continues, finding application in products for which the properties of organic materials can be exploited to the utmost such as organic transistors for electronic artificial skin. The field of organic molecular electronics, the foundation of which has been established by Dr. Inokuchi through these achievements, has the potential for even further development, and thus Dr. Inokuchi's pioneering contributions to the field are immense.

Notes
*1 Benzene ring: A regular hexagonal ring structure consisting of six carbon atoms, which is found in such aromatic compounds as benzene.
*2 Violanthrone: An aromatic compound whose molecules consist of nine fused benzene rings
*3 Perylene: An aromatic compound whose molecules consist of five fused benzene rings

For more details, see the Achievements.