Application And Research Of New Porphyrin Dimers In Dye-sensitized Solar Cells

Dye sensitizers are an important part of DSSC because they can collect photons and use the energy of photons for electron transfer and dye regeneration.Some metal-free dyes are currently under a lot of research because of their high molar extinction coefficient,low production cost,environmental friendliness,flexible molecular structure,and adjustable absorption properties,etc.Among the many sensitizers porphyrins are a class of natural and synthetic tetrapyrrole Among many sensitizers,porphyrins are a class of natural and synthetic tetrapyrroles,whose derivatives play an important role as light-harvesting antennas in the natural photosynthetic process.Functionalized porphyrin derivatives have been extensively studied in light harvesting processes,including energy transfer and electron transfer processes.However,on the one hand,the large conjugated structure of porphyrin dye molecules leads to his poor solubility and easy aggregation,and on the other hand,his incomplete light absorption in the infrared region causes the efficiency of DSSCs to lag behind that of organic and chalcogenide solar cells.In this paper,six zinc porphyrin antenna molecules（ZnP1-ZnP6）and ZnPA-anchored porphyrins were designed and synthesized for the construction of dye-sensitized solar cells.On this basis,DFT theoretical calculation is used to combine experiment and theory,and the structure-activity relationship between experimental results and material properties is deeply discussed.By modifying the structure of porphyrins,the photoelectric conversion efficiency of dye-sensitized solar cells can be effectively improved.The main research contents and results are as follows:1.The structural needles of 6 porphyrin dyes ZnP1～ZnP6 were carried out by 1HNMR,high-resolution mass spectrometry,ultraviolet-visible spectroscopy and other methods.The effect of this group on the photoelectric properties of DSSC was studied by improving the side chain groups of porphyrin molecules（thiophene,benzothiophene,thianthracene,and pyridine cation groups with different side chains）.2.The porphyrin dye ZnPA-ZnPi（i=1-6）was applied to DSSC to measure its optical properties and electrochemical impedance.The photoelectric conversion efficiency obtained was:ZnPA-ZnP3>ZnPA-ZnP1>ZnPA-ZnP2,indicating that porphyrins containin thianthracene groups showed relatively high efficiency,and the introduction of thianthracene groups had to broaden the absorption spectrum,which could enhance the light-harvesting ability of porphyrin dyes in visible and near-infrared regions,and ZnPA-ZnP3 showed maximum photoelectric efficiencyη=2.25%;Using DCCS experiments and theoretical analysis,ZnPA-ZnP6>ZnPA-ZnP5>ZnPA-ZnP4 were obtained by using DCCS experiments and theoretical analysis,and the results showed that the introduction of dodecoxy groups on pyridylporphyrins could inhibit the aggregation of dyes and significantly improve J_SC.Among them,ZnPA-ZnP6 has the highest photoelectric conversion efficiency（η=2.53%）.3.The density functional（DFT）method was adopted,and ZnPA-ZnPi（i=1-6）was used as the research object.The structural optimization shows that the ZnPA-ZnPi（i=1-3）configuration is an almost vertical structure,which indicates that the transport of electrons from porphyrins to TiO₂ conduction band is favorable.ZnPA-ZnPi（i=4-6）has also been studied,and the antenna porphyrin of the three self-assembled photosensitizers has a certain angle between the anchored porphyrin,and the structure is torsional,and this non-planar structure helps to inhibit the aggregation of dye.We also investigated the leading molecular orbitals of the dye ZnPA-ZnPi（i=1-6）.The results show that the electron cloud distribution of the HOMO orbit is mainly concentrated on the antenna porphyrin large ring,and the electron cloud of the LUMO orbital is distributed in the anchored porphyrin ring,anchored porphyrin pyridine group and anchored part of carboxylic acid group,which indicates that its electrons can be well transported.In orbital spectroscopy of ZnPA-ZnPi（i=1-6）,we found that all porphyrin molecules can efficiently inject electrons into the conduction band of TiO₂ and enable dye regeneration.In this paper,porphyrin molecules were designed and synthesized to investigate the effect of different structures of the molecules on the photovoltaic performance aspects,and the results all showed better photovoltaic properties.The structures of thiophene,benzothiophene,thianthrene,and pyridine cationic groups with different side chains significantly improve the photovoltaic properties of the cells.