Research on Novel Optoelectronic Devices with High Conversion Efficiencies Based on Surface Plasmon Excitation

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It is well known that metal surfaces can support so-called surface plasmon polaritons (SPP), which are localized at the surfaces and propagate along the surfaces as plane waves. When the SPP is excited, very strong electromagnetic fields are created near the metal surface and various kinds of enhancement effects such as the surface-enhanced Raman scattering are expected. In this research project, we applied such enhancement effects to obtain high conversion efficiencies in optoelectronic devices including solar cells, in particular, organic solar cells. Our experimental results demonstrate that the conversion efficiency of organic solar cells can be enhanced by a factor of 8 upon exciting the SPP by a conventional attenuated total reflection (ATR) technique. We also developed a new technique of the SPP excitation, which uses a layrof metallic fine particles. We demonstrated that using the interaction between the surface plasmons localized in the fine particles the with SPP propagating on the metal surfaces, it is possible to excite the SPP.Efforts was also made to improve the optoelectronic properties of ultra thin organic films. Optoelectronic characteristics of a variety of organic thin films and solar cells made of them were measured. Important factors which affects the conversion efficiencies were clarified. Results of the present studies can be applied to develop novel optoelectronic organic devices with high conversion efficiencies.