Synthesis, Self-assembly Behavior and Opto-electric Properties Of Porphyrin Derivatives Tethered by Fullerene C60.pdf

1、Porphyrins have attracted increasing attention due to their electrochemical and photophysicalproperties, which can be tuned upon insertion of different metal ions and by changing thesubstituent on the porphyrin core. The

2、se unique properties include photostability, intensephotoluminescence, large molar absorption coefficients, good light-harvesting, and highfluorescence quantum yield.Fullerene C60, on the hand is used as a spherical elec

3、tron acceptordue to their unique photophysical, electrochemical and chemical properties. Fullerene C60 hasbeen shown to reversibly accept up to six electrons in solution and accelerate charge separationand slow down char

4、ge recombination versus donor-acceptor (DA) dyads.The most importantfeature of porphyrins and fullerene C60 is that they spontaneously attract each other mainlythrough dispersive and donor-acceptor interactions.Therefore

5、, porphyrin as a donor andfullerene C60 as an acceptor seems an ideal combination for application in organic solar cells.
　　 This thesis focuses on the synthesis, spectroscopic studies and self-assembly behavior ofpo

6、rphyrin derivatives linked to fullerene C60, which included COOH groups in its fullerene unitso as to promote their anchoring onto TiO2 of the dye sensitized solar cells.Since the porphyrinderivatives-fullerene C60 dyad

7、molecules can interact with TiO2 nanoparticles using the COOHgroups in the fullerene unit, the photoinduced electrons produced by the porphyrin unit would betransferred to the fullerene C6o unit and from thence to the na

8、noporous TiO2.The fourcompounds in this research are 5-(4-hydroxyphenyl)-10, 15, 20-tri-(4-methylphenyl)-H2porphyrin(1), 5-(4-hydroxyphenyl)-10, 15, 20-tri-(4-methylphenyl)-Zinc-porphyrin (2), 4-methylphenyl-H2-porphyrin

9、-fullerene C60-COOH (3) and 4-methylphenyl-zinc porphyrin-fullerene C60-COOH (4).Their solution self-assembly has been widely studied, and opto-electricproperties have been researched.
　　 The synthesis and characteri

10、zation of a series of compounds in which porphyrin and fullereneC6o are coupled were done, in particular, the two series of compounds;free metallizationcompounds and zinc-metallization compounds.Characterization in solut

11、ion (1H NMR and 13CNMR spectroscopy) and FT-IR spectroscopy proves the identity of these compounds underinvestigation.
　　 The solution self-assembly and opto-electric properties of H2Por-OH (1) and H2Por-C6o-COOH (3)

12、 were investigated by UV-Vis absorption spectra, fluorescence spectra,electrochemical measurements and power conversion efficiency.The UV-Vis absorption spectraof H2Por-C60-COOH (3) exhibit a blue shift as compared to th

13、ose of H2Por-OH (1).The molarabsorption coefficients of the two compounds were more than 5.5x105 M-1 cm-1.There wasquenching in fluorescence intensity of H2Por-C60-COOH (3) as compared to that of H2Por-OH (1)at the same

14、concentration, suggesting a probable intramolecular electron transfer betweenporphyrin and fullerene C60.The electrochemical measurements showed that H2Por-C60-COOH(3) span narrower range (1.60 eV) than H2Por-OH (1) (2.5

15、5 eV), hence the electron transfer inH2Por-C60-COOH (3) is faster than H2Por-OH (1).The power conversion efficiency (η) valuewas further enhanced by introducing fullerene C60 in the porphyrin donor, whereby 0.49％ forH2Po

16、r-C60-COOH (3) and 0.18％ for H2Por-OH (1), which was about two times larger than thatof their corresponding porphyrin donor compound.UV-Vis absorption spectra and fluorescencespectra in single solvent and bi-solvent were

17、 used to study self-assembly behavior.Detailedspectral studies reveal that the two compounds showed polarity-dependent, solvent-dependentand temperature-dependent.The results showed that J-type aggregation occurred in ch

18、loroformat high concentration and/or at low temperature in toluene solution.
　　 Insertion of zinc ions into the core of the porphyrin donor tends to change the opto-electricproperties of their precursors.The solution

19、 self-assembly and opto-electric properties of ZnPor-OH (2) and ZnPor-C60-COOH (3) were investigated.The UV-Vis absorption spectra of ZnPor-C60-COOH (4) exhibit a blue shift as compared to ZnPor-OH (1).The molar absorpti

20、oncoefficients of the two compounds was more than 5.5x105 M-1 cm-1, hence they all exceed 1x105M-1 cm-1, which was the highest among the organic compounds.There was quenching influorescence intensity of ZnPor-C60-COOH (4

21、) as compared to that of ZnPor-OH (2) under the same concentration, suggesting a probable intramolecular electron transfer between zinc-porphyrin and fullerene C60.The electrochemical measurements showed that ZnPor-C60-C

22、OOH(4) span narrower range (1.40 eV) than ZnPor-OH (2) (2.30 eV), hence the electron transfer inZnPor-C60-COOH (4) is faster than ZnPor-OH (2).The power conversion efficiency (η) valuewas further enhanced by introducing

23、fullerene C60 in the Zinc-porphyrin donor, whereby 0.56％for ZnPor-C60-COOH (4) and 0.25％ for ZnPor-OH (2), which was about two times larger thanthat of their corresponding porphyrin donor compound.The UV-Vis spectra and

24、fluorescencespectra in single solvent and bi-solvent were used to study self-assembly behavior.Detailedspectral studies of the two compounds showed polarity-dependent, solvent-dependent andtemperature-dependent.The resul

25、ts showed that J-type aggregation occurred in chloroform athigh concentration and/or at low temperature in toluene solution.
　　 The power conversion efficiency (η) value was further enhanced by introducing fullerene

26、C60in the porphyrin donor, which is about two times larger than that of their correspondingporphyrin donor compounds.The H2Por-C60-COOH (3) gave efficiency (η) of 0.49％, whileZnPor-C60-COOH (4) gave efficiency (η) of 0.5

27、6％, these efficiencies are still low, which mayhave been caused by the presence of solvent impurity in the dye, dye aggregation or electronrecombination with oxidized dye molecules.The COOH group promotes the compound ad

28、sorptiononto the TiO2 yielding higher photocurrent per molecule by photosensitization process, which mayprobably prove that H2Por-C6o-COOH (3) and ZnPor-C6o-COOH (4) may have a potentiallyapplication in dye-sensitized so