Cation-controlled interfacial charge injection in sensitized nanocrystalline TiO{sub 2}
The photophysical and photoelectrochemical properties of Ru(deeb)(bpy){sub 2}(PF{sub 6}){sub 2}, where bpy is 2,2{prime}-bipyridine and deeb is 4,4{prime}-(CODEt){sub 2}-2,2{prime}-bipyridine, anchored to nanocrystalline TiO{sub 2}(anatase) or ZrO{sub 2} films are reported. In neat acetonitrile (or 0.1 M tetrabutylammonium perchlorate) long-lived metal-to-ligand charge transfer (MLCT) excited states are observed on both TiO{sub 2} and ZrO{sub 2}. Addition of LiClO{sub 4} results in a red shift in the MLCT absorption and photoluminescence, PL, spectra on both TiO{sub 2} and ZrO{sub 2}, and a concentration-dependent quenching of the PL intensity on TiO{sub 2}. The Li{sup +}-induced spectroscopic changes were found to be reversible by varying the electrolyte composition. Time-resolved adsorption measurements demonstrate that the presence of lithium cations increases the quantum yield for interfacial charge separation with no discernible influence on the rate of charge recombination. A second-order kinetic model quantified charge recombination transients. A model is proposed wherein Li{sup +} ion adsorption stabilizes TiO{sub 2} acceptor sites resulting in energetically more favorable interfacial electron transfer. The generality of this model was explored with different electrolytes and sensitizers. In regenerative solar cells, the addition of Li{sup +} increases both the efficiency and long wavelength sensitivity of the cell.
- Research Organization:
- Johns Hopkins Univ., Baltimore, MD (US)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 20013611
- Journal Information:
- Langmuir, Vol. 15, Issue 20; Other Information: PBD: 28 Sep 1999; ISSN 0743-7463
- Country of Publication:
- United States
- Language:
- English
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