| With the rapid development of human society, seeking the energy of sustainable, notsubject to regional restrictions, green and safe is the main development direction in thefuture. At present, solar cell attracts great attention because it is the main way to convertthe solar energy to electrical energy. Inorganic solar cell has been commercialized, but thehigh cost and complex process encourage people to focus on the organic one.Currently, polymer bulk heterojunction organic solar cell with P3HT as electrondonor and PCBM as electron accepter is the most seemly candidate because ofadvantages like inexpensive and easy-processing (spin-coating, jetting and printingwhich be suitable for mass production), but the photoelectric conversion efficiency is stillnot ideal. As the basis of organic solar cell, it is the key to design and synthesize theorganic active layer materials with excellent properties to improve the performances ofthe cell. The thesis studies the materials of organic solar cell based on polythiophenederivatives mainly for the donor materials based on P3HT as electron donor. Through thesynthesis of new polymers and doped them with P3HT， we broaden the adsorption ofthe solar spectrum which could lead to improve the photoelectric conversion efficiencyof organic solar cell.In this thesis, two target monomers and four polymers are synthesized and themolecular weight, ultraviolet spectrum, fluorescence spectrum,1HNMR spectroscopy, andcomputational simulation properties of them are studied. The relationship betweenmolecular structure and some properties is also discussed. It is hoped to lay the foundationfor the exploration of organic solar cell with better performance. The main contents of thethesis are as follows.Firstly, it provides detailed introduction on the action mechanism, structure, performance parameters of organic solar cells and the research progress of the materials.Secondly, two vinyl fluorene derivatives such as9,9-dibutyl-2-vinyl-fluorene and9,9-dihexyl-2-vinyl-fluorene are synthesized. The ultraviolet and fluorescent spectra aremeasured. The geometric structures and excited states are simulated with the DFT andTDDFT methods and they are basically the same to our experiment results. The structuresof the monomers are characterized and proved by1HNMR.Thirdly, with9,9-dibutyl-2-vinyl-fluorene and9,9-dihexyl-2-vinyl-fluorene asmonomers, two homopolymers of PBF and PHF are synthesized. Co-polymerized thetwo monomers with9-vinyl-carbazole respectively, two products named PBF-CaZ、PHF-CaZ are acquired. The copolymers are proved to be macromolecule by measuringthe molecular weight with GPC. The relationship between molecular structure andoptical performances of polymer with solution and film states are discussed by ultravioletand fluorescence technologies, respectively. The results show that the effect of carbonchain length on the ultraviolet adsorption is little. Compared to the monomers, the doublebond changing to a single one in polymerization reaction reduces the degree ofconjugation and leads to blue shrift of the maximum absorption peak of polymers. Theisolation effect of CH2on the ultraviolet absorption of copolymers is the overlay ofchromophores adsorption of fluorene and carbazole.Finally, PBF，PHF，PBF-CaZ and PHF-CaZ are doped with P3HT, respectively. Therelationship between molecular structure and optical performances of the blend films isdiscussed by ultraviolet technology. The absorption spectra of the films of PBF-CaZdoped with P3HT and PHF-CaZ doped with P3HT are the overlay of the adsorptionpeaks of fluorene, carbazole and P3HT. No other adsorption peaks and no position shriftbeing detected show that there is no interaction among the ground state of PBF-CaZ,PHF-CaZ and P3HT. The adsorption of copolymer is mainly below400nm while theadsorption range of P3HT is400to600nm. Therefore, blends of P3HT and targetpolymers can expend the adsorption range of the sunlight, which make it possible toimprove efficiency of present organic solar cells. |
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