| Dye-sensitized solar cells（DSSCs）have the advantages of strong stability,low cost and easy modification and regulation,so DSSCs have been widely studied and applied.Sensitized dye is a very significant part of DSSCs,and its structure has a great impact on the properties of molecules and devices.Although changing the structure of different groups is an effective means to control sensitized dyes,it will lead to the increase of research and development costs.According to our previous works,through molecular planarization,the energy levels can be selectively adjusted,while the light harvesting capability can also be enhanced.However,along with the improvement of planarity,the aggregation on the surface of the substrate,which bring serious problems to the cell devices.The introduction of steric groups into molecules can effectively prevent the aggregation.Thus,in this thesis,various steric groups are introduced into sensitizer and hole transport material molecules as the side chains groups.The structure-activity relationship between planarity and properties is systematically investigated through the characterization of photophysical,electrochemical,and other related properties.In Chapter 1,the working principles and the development of dye-sensitized solar cells and perovskite solar cells are briefly described.The research progresses of organic sensitizers with benzothiadiazole as the auxiliary acceptor and triphenylamine as the donor,is reviewed in detail,as well as the hole transport materials with twisted chemical structures.Then,the design ideas and the research content of this thesis are proposed.In Chapter 2,two sensitizers,coded as CS-75 and CS-76,with benzothiadiazole as the auxiliary acceptor group and triphenylamine as the donor group have been designed and synthesized.The chemical structures are characterized by 1H NMR,13C NMR and FT-IR.In Chapter 3,CS-60,CS-75 and CS-76 have been fully characterized through optical,electrochemical,and photovoltaic measurements.The absorption band is obviously blue-shifted thanks to the introduction of steric groups,while the molar extinction coefficient is also decreased.Due to the anti-aggregation capability arising from the steric groups,the blueshift of CS-75 is effectively shrunk after adsorbing on Ti O2surface.Meanwhile,the LUMO levels of CS-75 and CS-76 are selectively lifted,leading to the enlargement of the charge injection driving force.As a result,the charge injection efficiencies of CS-75 and CS-76 are efficiently enhanced compared with the reference dye CS-60.In Chapter 4,twisted hole transport molecules CS-78-CS-80 with different steric effect are designed and synthesized.The chemical structures of target compounds and all the intermediates are characterized by1H NMR,13C NMR and FT-IR.Along with the decrease of molecular planarity,the LUMO level is sharply downshifted and the band gap is enlarged,leading to the blueshift in absorption band of CS-79 and CS-80,compared with that of CS-78.After 30 times of redox test,CS-79 and CS-80 present no change between the 2nd and 30th tests,suggesting that the introduction of steric groups will not affect the electrochemical stability.Meanwhile,the thermal decomposition temperatures of CS-79 and CS-80 are higher than that of CS-78.That means the thermal stability is also improved as the decrease of molecular planarity.In Chapter 5,conclusions. |
