| Energy resource is the driving force and guarantee of social development. Along with the industry development and technique progress, the traditional fossil energy can hardly meet the human demands. At the same time, the using of traditional fossil energy brings the world serious environmental problems. Facing with the shortage of energy supply and problems of environmental pollution, scientists turn to the field of new energy. Solar energy attracts much interest and is being studied worldwide because of the huge energy stock and cleaning features.In all kinds of photovoltaic devices, hybrid solar cell is a kind of device which utilizes inorganic semiconductors as electron acceptor material and conjugated polymers as electron donor material. The manufacturing cost of hybrid solar cells is much lower than traditional silicon solar cells. The synthesis of such materials accompanies with the advantages of simple technique, lower energy cost, less environment polluting and suitable for flexible devices. Meanwhile, the photo-conversion efficiency can be tuned and improved while changing both the inorganic and polymer materials. With the advantages stated above, the inorganic semiconductor-conjugated polymer hybrid solar cells attract much attention in recent years and are developed very fast.When irradiated with sunlight, excitons will be genetated inside of the active materials. After that, photo-generated charges diffuse to the interface of semiconductor and conjugated polymer, dissociate at the interface and transfer to the opposite electrodes. Charge dissociation and transfer are two key taches in the process of photo-converting. In order to reduce the electron loss caused by the back recombination of photo-generated charges, the interface of inorganic semiconductor and conjugated polymer in hybrid solar cells should be improved. On one side, photo-generated charges can dissociate and transfer quickly and effectively through building unhindered pathways; on the other hand, improving the interaction at the interface can also promote the charge dissociation and transfer.On the basis of the above thoughts, this study combines one-dimensional nanomaterials and photo-initiated polymerization and synthesizes inorganic semiconductor-conjugated polymer photovoltaic materials. After preparation of nanocomposites via photo-initiated polymerization, photovoltaic performance and property of nanocomposites are researched and the main work and results are listed below:1. Hybrid materials of P25-Polythiophene are successfully obtained via photo-initiated polymerization, using TiO2(Degussa, P25) as the photo-catalyst and thiophene as the monomer. Spin-coated P25film is utilized in the polymerization and brown P25-PTh film is obtained. Through SEM and AFM, the surface of nanocomposite film is found to be flatter than that of neat P25film, indicating that the polymerization is an in-situ surface growth process.2. Raman and XPS methods are carried out on P25-PTh nanocomposite, the results show that strong interaction exists at the interface of TiO2and Polythiophene. The analysis of S2P and Ols XPS spectra indicate that Ti-S bond exists at the interface, this is the interaction formation in the nanocomposite.3. One-dimensional TiO2nanoarray film is synthesized through liquid phase deposition, using ZnO nanorod film as template. TiO2nanoarray film obtained is proved to be completely anatase phase. Diameter of the nanoarray is about100nm, while the nanoarray is longer than1μm. Meanwhile, not only nanorods but also TiO2nanotubes are found which is caused by the etching of ZnO template in the process of TiO2growth.4. TiO2nanoarray film is used in photo-initiated polymerization and brown one-dimensional TiO2-PTh nanocomposite film ("1D TiO2-PTh" in short) is successfully synthesized. It is found that nanopores of the nanoarray are gradually filled with polythiophene, as the irradiated time lasts. Photo electrodes are fabricated with the nanocomposite films. The result of the photocurrent shows that nanocomposite film performs best when the nanopores are filled exactly.5. Photovoltaic devices are fabricated with TiO2-PTh nanocomposite films through both photo-initiated polymerization and spin-coating. Results show that devices fabricated with TiO2nanoarray show photo-conversion response both in ultra and visible region. Meanwhile, the devices exhibit larger fill factors (>0.6). This is thought to be caused by the fact that electron can transfer through TiO2nanoarray quickly and thus reduce the recombination probability. On the other hand, nanocomposite films through photo-initiated polymerization show twice photo-conversion efficienty than that of spin-coated films. This is thought to be attributed to the higher pore filling and strong interaction at the interface which is caused by the mechanism of the photo-initiated polymerization.6. ZnO nanoparticles are grown on the surface of single-wall nanotubes through sol-gel method. The obtained nanohybrids are utilized in photo-initiated polymerization to copolymerize N-vinylcarbazole (NVK) and methyl acrylate (MA). Ternary ordered nanocomposite is obtained and continuous film on ITO glass is obtained through spin-coating technique.7. The synthesized ternary ordered nanocomposite is applied in photovoltaic devices. Results show that the incorporation of CNT with proper weight ratio enhances the photo-conversion performance effectively. Photoluminescence spectra is applied to research the charge transfer process in ternary-ordered nanocomposites, results show that electrons excited on the surface of PVK can not only transfer to ZnO, but also to the surface of CNT directly, thus promote the charge dissociation and transfer of photo-genetated charges. |
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