Synthesis And Properties Of D-D-π-A Triphenylamine Bridged Carbazole-based Photosensitive Dyes

As a new type of solar cell,dye-sensitized solar cells have become one of the hot spots in the field of solar energy utilization in recent years.In 1991,this type of battery was invented by the research group of Michael Gr?tzel who were worked in the Swiss federal Institute of Technology in Lausanne.Dye-sensitized solar cell is a typical representative of the third generation solar cell,which has many advantages,such as low raw material cost,diverse structure of dye sensitizers and excellent light absorption capabilities.The preparation of dyes is simple and not easy to cause environmental pollution.In this thesis,six new linear D-D-π-A triphenylamine bridged carbazole-based pure organic photosensitive dyes T1～T6 were designed and synthesized.Each dye molecule has two electron-donating groups,one electron-accepting group and one bridge.Triphenylamine group and carbazole group are the two electron-donating groups.Cyanoacetic acid is the electron-accepting group.Thiophene group,3,4-ethyldioxythiophene group and furan group are the bridge groups.Vilsmeier reaction,Sodium borohydride reduction,Transesterification reaction,Horner reaction,Suzuki reaction and Knoevenagel reaction were used to synthesize the six dyes T1～T6.The dyes T1～T6 and intermediates have been characterized and the structure is correct.The UV-Vis absorption spectra of six dyes T1～T6 were tested and it was found that the dyes T1～T6 had good spectral absorption in the visible region.The maximum absorption peak was in the range of 357 nm～370 nm.It can be seen that when the electron accepting group and the bridge group are the same,the exchange positions of the two electron donor groups triphenylamine group and carbazole group will form different dyes,among which the spectral absorption ranges of dyes T1,T2 and T3 are wide.Triphenylamine as a primary electron donor and Carbazole as a secondary electron donor perform better than carbazole as a primary electron donor and triphenylamine as a secondary electron donor.The third absorption peak positions of dyes T3 and T6 were significantly blue-shifted compared to dyes T1,T2,T4,and T5.It showed that the thiophene group and the 3,4-ethyldioxythiophene group were stronger than the furan group as aπ-bridge in broadening the absorption range of the dye.The test results of the electrochemical properties of dyes T1～T6 showed that the LUMO energy levels were between-1.81 V and-1.25 V,which were lower than the energy level of the Ti O2 conduction band（-0.5 V）.The HOMO energy levels were between 0.87 V and 1.02 V,which were higher than the redox level（0.4 V）of the iodine electrolyte and the redox level（0.57 V）of the cobalt electrolyte.Therefore,these six dyes T1～T6 meet the requirements of the energy level of dye-sensitized solar cells.The LUMO energy level of dye T2 is the highest,and its energy level difference E_0-0is the smallest,indicating that the spectral response range of dye T2 is the widest.The dyes T1,T2,T4 and T5 were made into dye-sensitized solar cells.The results of photovoltaic performance tests showed that under the simulated solar radiation of AM 1.5,they all showed a high photoelectric conversion efficiency,ranging from 3.74%to 6.00%.Among them,the photoelectric conversion efficiency of dye cell T2 was up to 6.00%,which has a high consistency with the light absorption performance of the T2 dye,showing a good application prospect.