Design And Synthesis Of Meso-substituted Small Molecular Porphyrins And Their Photoelectric Properties

The photosynthesis of green plants can efficiently convert solar energy into chemicalenergy that people could take use of. During this process, the chlorophyll plays a vitalrole in the absorption of solar cell and charge transfer. In this thesis, we choose thefundamental structural unit of chlorophyll-porphyrin as the research object, andanticipate that relationships between structures and properties of porphyrins could bepreliminary established, which will further provide new ideas for the material designsof high-efficient organic solar cells (OSCs).Porphyrin derivatives has strong absorption of sunlight in near ultraviolet area (400~500nm) and visible light area (500~700nm), moreover they own good light, heatand chemical stability, and high molar absorption coefficient, thus ensuring a broadprospect of porphyrins in the application of OSCs. Currently, great achievements havebeen made on the applications of porphyrins on OSCs. The power conversionefficiency (PCE) of porphyrin monomer based dye sensitization solar cells (DSSCs)reached13%, whereas the PCE of small-molecular porphyrin based heterojunctionOSCs reached7%. But in the design for porphyrin materials applied in OSCs, with the purpose of adjusting the solubility, migration rate and energy levels of porphyrinmolecules at the same time, researchers had to introduce different groups onto themeso-positions of porphyrin molecules, and the structures of the substituent wereoften complex. This would lead to tedious synthetic routes and low production rates,restricting further developments of porphyrin materials in organic photovoltaicdevices.To solve these problems of application of porphyrins on OPVs, herein, we carried outour experiments on the following perspectives:Firstly, a series of centre metal (II) substituent5,10,15,20-tetra(4-N,N-diphenylaminophenyl) porphyrins (P) were designed and synthesized.Incorporated flexible and strong electron-donating triphenylamine substitute endowedporphyrins with enhanced solubility and intermolecular interactions. The distinctionsof the properties arising from different centre metal ions were investigated byabsorption spectra, electrochemistry behavior, charge transport property, thermalstability, and morphology characterization. The Pd (II)5,10,15,20-tetra(4-N,N-diphenylaminophenyl) porphyrins (PPd) was found to represent morematching energy levels with [6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM),but with higher hole mobility and longer triplet exciton lifetime. Bulk heterojunctionsolar cells based on porphyrins and PC61BM had been fabricated, of which PPdbasedsolar cells exhibited greatly enhanced photovoltaic performance as a result of multipleelements. This will enlighten the future molecular designs of porphyrins applied inorganic small molecule bulk heterojunction solar cells.Secondly, we demonstrate the concept of controlling phase separation behaviorthrough designing directional intermolecular interactions. The twisted molecularconfiguration and intermolecular hydrogen bonds endow PBI-1self-assembly intonanofiber aggregates on order of tens of nanometers. In the blend of Zn-mTNP andPBI-1, the charge transfer interaction was suppressed effectively due to the unfavored π-π stacking for their twisted and planar molecular configurations. The spin-coatedfilms of Zn-mTNP, PBI-1and their blend have been characterized by UV-visabsorption spectra, and atomic force microscopy, revealing that preferred phaseseparation structures in nano scale was obtained.Thirdly, we choose porphyrins substituted by electroactive groups as electro-polymerization (EP) precursors. On the one hand, we fabricated polymer films ofZn-mTNP and Zn-mTCPP on the ITO substrate to serve as the anodic interfacemodification layer of OSCs, finding that the EP films of porphyrins could adjust thework function of the interface. On the other hand, EP films of Pt-mTNP was preparedas the support layer of precious metals (Pt) in the process of catalytic oxidation ofmethanol, and we found that the polymer films of porphyrins effectively enhance thecatalytic efficiency of the electrode. In all, we studied the EP behaviors of porphyrinssubstituted by electroactive groups, and further intended to preliminarily explorationthe relationships between the structure and properties of EP films of porphyrins.