Synthesis Of Phenothiazine Dyes With Alkoxy Chains And Their Applications In DSSC

Dye-sensitised solar cells(DSSC)are generally regarded as a promising solar cell technology due to facile fabrication process,low cost and environmental friendliness.In DSSC,the dye sensitiser is very important,and can decide the device performance.In this thesis,we designed and synthesised four pure organic dyes(TP1,TP2,TP3 and TP4)wth triphenylamine(TPA)as the donor,phenothiazine(PTZ)as the?-bridge and cyanoacrylic acid as the anchoring acceptor,and introduced hexyloxy or hexylphenyl into the donor or bridge,and investigated their absorption spectra and electrochemical properties,and their applications in DSSCs.The main contents are as follows:Firstly,theoretical calculations of the four dyes.Firstly,the feasibility of the designed molecules was demonstrated by optimising the molecular conformation and simulating the UV absorption spectra.The relationship between the structure and properties of the dye molecules is also revealed from the perspective of theoretical calculations by investigating the molecular electrostatic formulae,dye regeneration,charge recombination and density of states.It is shown that the hexoxyphenyl-modified bridge increases the light absorption capacity of the molecule and weakens the charge recombination effect,while the hexoxyl-modified donor not only promotes the absorption spectrum red-shifted,but also reduces the light capture efficiency and exacerbates the charge recombination effect.Secondly,the synthesis,characterization and properties of the four dyes.The dyes TP1,TP2,TP3 and TP4 were synthesised and their molecular structures were confirmed by ¹H NMR,¹³C NMR and MALDI-TOF.We investigated the photophysical and electrochemical properties through UV-Vis absorption spectrum and Cyclic Voltammetry.The results showed that all four dyes have good absorbance and suitable HOMO and LUMO energy levels,and can be used in DSSC.Among them,TP2 dye exhibit the strongest ICT absorbance in 461 nm.Thirdly,DSSC devices properties.With these four dyes as photosensitizer,with Ti O₂ prepared by electrostatic spraying as photoanode,with I^-/I₃^-as electrolyte,we investigated their DSSC devices and discussed their property difference.Using TP2 dye resulted in dye-sensitized solar cells that exhibit a high open-circuit voltage V_OC of 0.85 V,short-circuit current density J_SC of 12.77 m A cm^-2,fill factor of 0.6 and a power conversion efficiency of 6.59%.We also investigated the dye adsorption,open-circuit voltage decay and electrochemical impedance spectroscopy of the four dyes.The results showed that hexoxyphenyl chains can reduce the charge recombination effect better than hexyl chains to modify the?-bridge,thus improving the electron transition and ICT process;the hexyloxy chain modification of the donor improves the electron-donating ability,but also accelerates the charge recombination,thus shortens the electron lifetime,and reduces the dye loading,which in turn reduces the photoconversion efficiency of the device.