| In the effective utilization of the renewable energy, solar photovoltaic usage is the fastest growing and most dynamic area. The research and application of solar cell have been paid more attention by countries around the world. At present, solar cell is mostly on the basis of silicon material and inorganic compound.Their application is limited because of the complicated producing processes, high production cost. In order to improve the performance of solar cell, to lower manufacturing cost, to reduce the impact on the environment owing to large-scale production, scientists explored many new materials and new structure of solar cell. Organic polymer solar cell has many advantages such as the low price in raw material,simple production process,flexibility,reel-to-reel coating and so on. So it is paid attention to by researchers.At present, its conversion efficiency is still relatively low. One of the important factors which influence performance of organic polymer solar cell is photointuced charge tranfer.Carbon nanotubes have good charge transfer capability, they have been widely used to fabricate opto-electronic devices such as field effect trainsistor, organic photovoltaic cell etc. Polyaniline is more excellent on account of its good electrical conductivity and absorption within UV-visible and near infrared spectral region in the conducting polymers. Polyaniline becomes the hot research as a new organic solar cell material. Polyaniline and carbon nano tubes are respectively used as an electron donor material (D) and an electron acceptor (A) which are made of composite film. Micro-Interpenetrated network structure is formed by controlling the reaction condition. The D/A interface area in composite is increased, and the transfer of charge is expected to increase.The main investigating contents included:1.Carbon nanotubes were purified with the mixed acid which is composed of 75%concentrated sulfuric acid and 25%concentrated nitric acid (volume ratio). Carbon nanotubes before and after purification was characterized. Scanning electron microscopy (SEM), Raman spectroscopy (Raman), X-ray diffraction (Xrd) study show that purity is improved, and the purified carbon nanotubes grafted hydroxyl and carboxyl functional groups on the wall through FTIR spectra analysis.2.Dispersion of carbon nanotubes were observed by Ultrasonic oscillations of carbon nanotubes in organic solvent dimethylformamide. Carbon nanotubes formed a good dispersion. The composite with different mass fraction of carbon nanotubes was prepared by blending and in-situ polymerization.3.The composite was dispersed in organic solvent dimethylformamide, and then the film of composite was prepared by dip-coating method on glass substrate. It was dried at 50℃.The surface and section morphology of film was studied by SEM. Composite films prepared by situ polymerization was dispersed more evenly than blending, and thickness of composite film is about lμm. The light absorption of composite films prepared by situ polymerization was characterized by UV-visible spectrophotometer.4.The electrooptical properties of composite films were tested by four-probe resistivity meter, it was discussed that the content of carbon nanot ubes, ultrasonic time, preparation method, thermal annealing influenced on the conductivity of composite films.The conductivity varies from 1.6×10-2s/cm to 120x10-2s/cm with the increasement of MWNT concentration. An intense interaction exists between MWNT and PANI, andπ-πconjugate is formed between delocalized electrons of carbon nanotubes andπelectron on the main chain of PANI. The effective conjugate length of main chain is increased under light radiation. So the conductive of composite film is improved. |
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