Electronic and Optical Functionality and Photovoltaic Application of Conducting Polymer-Fullerene-Nanotube Composite

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Photo-excitation dynamics and interactions between polarons in concucting polymers and its interaction with fullerene and carbon nanotube have been studied, and highly efficient photovoltaic properties and novel functionality have been investigated.Composite systems of conducting polymers doped with fullerene and nanotube have been prepared, and their ground state and photo-excited state have been discussed from the results of optical and electrical properties. Utilizing substituted fullerenes and an endohedral metallofullerene, the efficient photo-induced charge transfer could be observed in the molecular systems with conducting polymers, and the photovoltaic properties depending on the substituents of fullerene have been found.Kinetics of decay of polaron pairs as precursors of free charge carriers at photoexcitation of poly(3-octylthiophene) under applied electrical field have been observed directly within a picosecond time domain by using the two-correlated-pulse laser technique. E … More xperiments have shown that polaron pairs were generated without any noticeable delay after the light absorption. At high enough excitation intensity, free charge carriers have been shown to take part in the second-order processes photocurrent produced by the recombination of two neighboring polaron pairs. It has been clarified that polaron pairs with two kinds of lifetimes exist and the decay time decreases by high electrical field strength, and that polaron pair is the main origin of the second-order photocurrent. The direct observation of photoluminescence within a picosecond time domain has been also discussed.Photovoltaic properties of a photovoltaic cell with a fullerene/conducting polymer heterojunction in the photovoltaic cell fabricated by spin-coating the solution of conducting polymer onto the fullerene thin film formed on ITO. Fabricated by this process, the photovoltaic cell has demonstrated the high efficiency for solar cells based on conducting polymers. From the optical properties of fullerene/conducting polymer heterojunction and the direct surface observation by using scanning electron microscope and atmic force microscope, it has been clarified that the interpenetrating interface of fullerene and conducting polymer contributes to the high photovoltaic performance.Surface morphology of fullerene films fabricated by vacuum deposition was modified by a spin-cast treatment process with various organic solvents used in the, and a nano-rod-shape surface has been obtained in the case of spin-cast treatment with trans-1,2-dichroloethylene. The field emission properties of fullerene films, the surface of which were modified, have been found to depend on the surface morphology. Less