Synthesis And Photovoltaic Properties Of Organic Dyes Containing Large Conjugated Structures Of Dibenzophenazine And Pyrene

Solar cells can directly convert solar energy into electrical energy,which is an effective way for the development and utilization of solar energy.Among solar cells,dye-sensitized solar cells(DSSCs)are a very promising new type of solar cell.As the key components of DSSCs devices,sensitizers are the center of photoelectric conversion and charge separation,and have received extensive attention.Organic sensitizer has been widely researched and developed due to their easy to synthesize and separate,ease of structure modification and high conversion efficiency.In this thesis,two series of 11 dye molecules were designed and synthesized,and the relationship between their molecular structure and the performance of DSSCs was discussed from the aspects of electron donor and p-bridge of sensitizers.The specific research works are mainly based on the following parts:1.Three novel dithieno[3,2-f:2',3'-h]quinoxaline-based organic dyes(IQ-C,IQ-D and IQ-F)with three ?-spacers were synthesized and developed for dye sensitized solar cells,where dithieno[3,2-f:2',3'-h]quinoxaline was used as electron-withdrawing ?-spacers,and 2,3-diphenylquinoxaline or dibenzo[a,c]phenazine as auxiliary electron-withdrawing ?-spacers.And six novel sensitized dyes of PT1-6 with double D-?-A branches(PT1-3)and single D-?-A branches(PT4-6)were synthesized and applied in dye sensitized solar cells.2.Photophysical and electrochemical properties of sensitizers were analyzed by UV-visible absorption spectroscopy,fluorescence emission spectroscopy,cyclic voltammetry,density functional theory calculation.And the performance of the DSSCs were characterized by monochromatic photon-to-current conversion efficiency(IPCE),J-V curve,and electrochemical impedance(EIS).3.The dye IQ-D with 2,3-diphenylquinoxaline as auxiliary electron-withdrawing ?-spacer exhibited higher photocurrent(Jsc)and photovoltage(Voc)than that of the dye IQ-C with 2,3-bis(4-(octyloxy)phenyl)quinoxaline as the additional electron-withdrawing ?-spacer,due to the larger adsorption amount of IQ-D.The dye IQ-F with a rigid conjugated dibenzo[a,c]phenazine as additional electron-withdrawing ?-spacer showed the highest efficiency of 6.54% under AM 1.5 G irradiation.It was demonstrated that the ?-spacersinfluence the photovoltaic performance of the dithieno[3,2-f:2',3'-h]quinoxaline-based organic dyes significantly.The results indicated that the dyes with three ?-spacers are promising candidates for efficient dye-sensitized solar cells.4.The photoelectric conversion efficiency of a single branched dyes increases as the conjugate extension of donor,and PT4 achieves the highest efficiency of 6.71% in single branched dyes.And the power conversion efficiency(PCE)of PT1 and PT2 is higher than that of the corresponding single branched dyes(PT6 and PT5).This advantage can be attributed to the fact that the double branched dyes have a higher number of light-harvesting units on the Ti O2 film.However,the double branched dyes have a higher tendency to aggregate as the conjugate of donor is extended,so the efficiency from PT1 to PT3 is reduced.And the double branched dyes of PT1 achieves the highest efficiency of 7.75% among the six sensitized dyes.