Elucidation and Control of Interfaces Related to Organic Electronic Devices

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1. UPS study of highly ordered organic films gave very sharp spectral features, leading to the clarification of change of electronic structure by molecular order and charge transfer rate at organic/metal interface. We also observed the splitting of the molecular levels for pentacene on clean metal surfaces, and the energy band dispersion could be determined.2. Possible band bending was systematically examined for organic semiconductors which are usually used nominally undoped, in contrast to inorganic semiconductors. The results revealed that bending does not occur for some cases, and that appropriate doping can be used to cause and control the bending, e.g. for enhanced carrier injection.3. The electrical characteristics of organic semiconductors are much affected by atmosphere (e.g. air and O_2). The study of such effect for titanyl phthalocyanine from the viewpoint of interfacial electronic structure showed that oxygen converts the downward bending of films prepared in ultrahigh vac … More uum (HV) to upward bending, This was ascribed to the doping by oxygen working as acceptor.4. New apparatuses of electrical measurements, were developed for under various environments from UHV to gas atmosphere, including thermopower, and displacement current, and detailed Information, e.g. on carrier injection was obtained.5. New methods for examining the electronic structures of organic films were developed, including photoelectron microscopy, high-resolution inverse photoemission, and X-ray emission spectroscopy.6. Complex phenomena at organic interfaces, e.g. motion of organic molecules, diffusion of metal atoms in organic films, and giant surface potential formation, were found and clarified.7. Theoretical calculations were performed on the electronic structure of organic/metal interfaces and the change of metal work function by deposition of organic molecules. They gave good agreement with experimental results.8. Electronic structures of new organic semiconductors and ionic liquids, which attract attention as new electrolyte for organic solar cell, were determined. Less