Fabrication of Organic Solar Cell by Using Materials having Different Carrier Diffusion Constant

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The development of organic solar cell requires to solve such issues as, (1) deposition of thin organic films that have high carrier mobility or photo-sensitivity, (2) stacking of organic layers that have carrier transport capability of different charges, (3) thermal stability of the stacked structure, (4) formation of electrode for electron injection into the stacked structure from outer circuit, etc. This research intends to investigate the first three items from the viewpoint of film formation technology, i. e., through the deposition polymerization of carrier transport layers. The fourth item was investigated by the formation of carrier injection layer that has high carrier injection efficiency into the organic layer.Regarding the deposition polymerization, it has been shown that thermally stable polyimide thin films can be obtained without using solvents by the co-deposition of perylenetetracarboxyjic dianhydride and several diamines. The film is expected to have charge transport c … More apability and high optical absorption coefficient coming from the perylene unit. It was also shown that polyurea thin films having azobenzene unit as photoreceptor can be prepared by the co-deposition of azo-containing diamine and diphenylmethane diisocyanate. The dipole orientation of the azobenzene unit can be controlled by the bias voltage on the substrate during the film formation. π-conjugated polymer thin films can be deposited by the co-deposition of biphenylaldehyde and diaminonaphthalene. The film was found to have high conductivity. By the iomzation-assisted deposition of an acrylate monomer that has tetraphenyldiaminobiphenyl unit, hole-transporting polymer thin films were obtained. Since these films can be obtained without solvents, they can be easily stacked with electron transport materials for fabricating organic thin film devices.As for the carrier injection layer, strontium or strontium oxide ultra thin films were prepared at the interface of the cathode and the organic layer. The films were deposited by the ionization-assisted method to the thickness of several nanometers. This method brought about a remarkable improvement of electron injection to the organic layer from the aluminum cathode. Less