Charge recombination in dye-sensitized nanocrystalline TiO{sub 2} solar cells
- National Renewable Energy Lab., Golden, CO (United States)
- Ecole Polytechnique Federale, Lausanne (Switzerland)
Charge recombination between dye-sensitized nanocrystalline TiO{sub 2} electrodes and the I{sub 3}{sup -}/I{sup -} couple in nonaqueous solution is described. The sensitizer was [RuL{sub 2}(NCS){sub 2}] (L = 2,2`-bipyridyl-4,4`-dicarboxylic acid). An apparent inequality between the dark current and the recombination current is ascribed to a voltage shift caused by a potential drop at the SnO{sub 2}/TiO{sub 2} interface, ohmic losses in the SnO{sub 2} and TiO{sub 2}, and an overpotential for the redox reaction at the Pt counter electrode. Treating the dye-coated TiO{sub 2} electrodes with pyridine derivatives (4-tert-butylpyridine, 2-vinylpyridine, or poly(2-vinylpyridine)) improves significantly both the open-circuit photovoltage V{sub oc} (from 0.57 to 0.73 V) and the cell conversion efficiency (from 5.8 to 7.5%) at a radiant power of 100 mW/cm{sup 2} (AM 1.5) with respect to the untreated electrode. An analytical expression relating V{sub oc} to the interfacial recombination kinetics is derived, and its limitations are discussed. Analysis of V{sub oc} vs radiant power data with this expression indicates that the pyridine compounds may lower the back-electron-transfer rate constant by 1-2 orders of magnitude. The pyridines are found to have no significant effect on the recombination mechanism and kinetics of electron injection from excited dye molecules to TiO{sub 2}. 40 refs., 9 figs., 1 tab.
- DOE Contract Number:
- AC36-83CH10093
- OSTI ID:
- 535434
- Journal Information:
- Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Journal Name: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical Journal Issue: 14 Vol. 101; ISSN 1089-5647; ISSN JPCBFK
- Country of Publication:
- United States
- Language:
- English
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