Preparation And Photovoltaic Properties Of Coumarin-Porphyrin Bi-Photosensitizers

Dye-sensitized solar cells (DSSC) have attracted significant attention in recentyears.Porphyrins due to their strong Soret (400-450nm) and moderate Q bands(550-600nm) absorption properties as well as the vital roles of porphyrin derivativesin photosynthesis have attracted more attentions. On the other hand, coumarins(2H-1-benzopyran-2-one), considering their excellent electron donating abilities, havealso been used as photosensitizers in DSSCs. In this paper, we first introduced the twochromophores,5,10,15,20-tetraphenylporphyrin unit and substituted-coumarin unit, asa bi-photosensitizer for DSSC.Meso-coumarin-porphyrin compounds (RC1-RC3), meso-coumarin-porphyrinbi-photosensitizers (PC1-PC3) and β-coumarin-porphyrin bi-photosensitizers(βPC1-βPC3, βPC1-βPC3’) have been designed and synthesized. The compoundshave been detected by~1H-NMR, MASS, UV-vis spectra, emission spectra, andphotocurrent-voltage (J-V) characteristics.5,10,15,20-tetraphenylporphyrin (TPP) was prepared by Alder method, then bynitration and reduction,5-(4-aminophenyl)-10,15,20-triphenylporphyrin(ATPP) wasobtained. ATPP was reacted with4-formyl-coumarins to gain themeso-couamrin-porphyrin schiff bases(TC1-TC3), which was then reduced to givemeso-coumarin-porphyrin compounds (RC1-RC3). We also try to introduce the estergroup to the molecular,but did not get the target compound.meso-coumarin-porphyrin bi-photosensitizers (PC1-PC3) have been synthesizedusing TC1-TC3as the starting materials. Make use of the1,3-dipolar cycloadditonreaction between TC1-TC3, and(E)-methyl-4-(chloro(hydroxyimino)methyl)benzoate, the ester group was introducedinto the molecular. Then treatment with zinc acetate and by hydrolysis,meso-coumarin-porphyrin bi-photosensitizers (PC1-PC3) were obtained. PC1-PC3sensitized cells exhibit1.23%,=1.33%,and=1.22%, respectively, and the lowefficiencies may due to the non-conjugated structure of the5-membered heterocyclicring, which may hinder the electron transfer from the dyes to TiO2surface.The β-porphyrin triphenylphosphine has been prepared by formylation, reduction,chloromethylation and condensation of TPP. Then couamrin units was introducedthrough the wittig reaction between porphyrin triphenylphosphine with 4-formylcoumarins. The ester group was introduced through1,3-dipolarcycloadditon reaction, and then treatment with zinc acetate and by hydrolysis,-coumarin-porphyrin bi-photosensitizers (βPC1-βPC3, βPC1-βPC3’) were obtained.βPC1-βPC3, βPC1-βPC3’ sensitized cells exhibit0.89%,=0.91%,,=0.76%,and0.89%,=0.70%,,=0.79%respectively. The the low efficiencies may alsodue to the non-conjugated structure of the5-membered heterocyclic ring, which mayhinder the electron transfer from the dyes to TiO2surface.