Femtosecond transient absorption of zinc porphyrins with oligo(phenylethylnyl) linkers in solution and on TiO2 films

Chih Wei Chang, Liyang Luo, Chung Kung Chou, Chen Fu Lo, Ching Yao Lin, Chen Shiung Hung, Yuan Pern Lee, Eric Wei Guang Diau

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Abstract

We measured femtosecond transient absorption of dye solutions and TiO 2 films sensitized with two zinc porphyrins (PE1 and PE4) to investigate the interfacial dynamics of electron transfer in relation to the dependence of cell performance on the length of the linker (Lin, C.-Y.; Lo, C.-F.; Luo, L.; Lu, H.-P.; Hung, C.-S.; Diau, E. W.-G. J. Phys. Chem. C 2009, 113, 755-764). For both porphyrins adsorbed on TiO2 films with S 1 excitation (λex = 620 nm), the transient absorption kinetics probed at 630 nm and 4.9 μm are complementary to each other because only the excited-state and ground-state species were observed at 630 nm whereas only the charge-separation intermediates were observed at 4.9 μm. The transient of the PE1/TiO2 film shows a single exponential decay with a large offset, whereas the transient of the PE4/TiO2 film displays a biexponential decay with a small offset. Because of the existence of an additional ps component, the amount of free delocalized electrons (offset signal) in PE4/TiO2 is smaller than that in PE1/TiO2. Our results imply that back electron transfer at the TiO2/dye interface is an important factor to be considered to account for the cell performance of a device.

Original languageEnglish
Pages (from-to)11524-11531
Number of pages8
JournalJournal of Physical Chemistry C
Volume113
Issue number27
DOIs
Publication statusPublished - 2009 Jul 9

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All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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