| In recent years,with the high speed development of display technology,liquid crystal materials hold a pivotal position in the display mode because of its especially excellent performance.In addition,so many researchers are constantly optimizing the structure and performance of liquid crystal molecules and give it a new role in order to play a huge role in the field of industrialization,such as aerospace,bio-medicine,thin-film solar cells and dye-sensitized solar cells.Based on the years of study of liquid crystal materials(LCs)and dye-sensitized solar cells(DSSCs)in our laboratory,it is possible to design a molecule which has a certain liquid crystal performance(can be applied to TN display mode and IPS display mode)and can be used in dye-sensitized solar cells as a dye sensitizer,then broaden the scope of application of liquid crystal molecules.In this paper,two series of liquid crystal molecules were synthesized(introduced some functional groups,such as pyridine,trans-cyclohexane,ethylene bridge bond,thiophene,side-fluoro and etc.),which were based on the structure of rod-shaped liquid crystal molecules.Additionally,we intestigated liquid crystal properties and dye performance of all the products.The results showed that our products not only have nematic phase but also have the functions of dye sensitizers,and these compounds have not been reported in domestic and foreign literature.The main research contents are as follows:1.Seven new pruducts were synthesized from 1-bromo-4-iodo-benzene,4-boronic acid-pyridine,4-iodo-pyridine,2,5-dibromothiophene,trimethylethanol,trimethylethylsilyl and other compounds via a series of classic reactions,involving Sonogashira reaction,Suzuki reaction and "One pot method" reactions.The structures of target compounds along with their intermediates were confirmed by mass spectroscopy(MS),elemental analysis and infrared spectroscopy(IR),nuclear magnetic resonance(NMR).2.By DSC and POM,We found that C6-1,C6-2 and C12-2 in series 1 did not show the expected liquid crystal phase.But 3N-1,3SN,3FN and 3FSN in series 2 showed a wide nematic phase during the temperature of rise and fall aides.It was found that the introduction of fluorine in the side position can effectively reduce the melting point of liquid crystal molecules,broaden the interval of liquid crystal nematic phase,and the introduction of thiophene will narrow the interval of mesophase.3.By studying the spectral performance,we found that two series of target compounds showed a significant near-ultraviolet absorption band in the wavelength of 300～400nm.In the series of 2,the introduction of fluorine and thiophene enhanced the degree of molecular conjugation,so that the maximum absorption peak redshift.There was a strong fluorescence emission spectrum in the range of 400～500nm,but the introduction of thiophene greatly attenuates the fluorescence absorption intensity of the compound.4.Measurements of electrochemical properties showed that the ELUMO and EHOMO of C6-1,C6-2,C12-2 and 3N-1,3FN,3SN,3FSN meet the basic requirements of DSSCs for dye sensitizers.It was found that the optimized structures of 3N-1,3FN,3SN,and 3FSN basically maintain the configuration of rod-like molecules,and the HOMO and LUMO levels overlap in large area,which is beneficial to the election transition of the dye molecules after irradiation.Because of the solvent effect,the Eg of the DFT calculation is larger than the Egec measured.5.By studying the photovoltaic properties and impedance properties,we found that the open circuit voltage(Voc=500.19 mV),the short-circuit current density(Jsc ＝0.4196 mA cm-2),the filling factor(FF=0.5614)and the photoelectric conversion efficiency of C12-2 in series 1 reached the maximum value,Indicating that the position of the acetylenic bond and the change of the length of the alkyl chain will significantly affect the photoelectric properties of the dye.The introduction of side fluorine and thiophene in series 2 can significantly increase the short-circuit current density of DSSCs.3FSN also achieves a relatively high photoelectric conversion efficiency(0.10%)due to its relatively highest short-circuit current density and open circuit voltage. |
