Comparison of Dye-Sensitized ZnO and TiO2 Solar Cells: Studies of Charge Transport and Carrier Lifetime
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- 作者：Marí ; a Quintana ; Tomas Edvinsson ; Anders Hagfeldt ; Gerrit Boschloo
- 刊名：Journal of Physical Chemistry C
- 出版年：2007
- 出版时间：January 18, 2007
- 年：2007
- 卷：111
- 期：2
- 页码：1035 - 1041
- 全文大小：255K
- 年卷期：v.111,no.2(January 18, 2007)
- ISSN：1932-7455
文摘
Nanocrystalline particles of ZnO and TiO2 of approximately equal size (~15 nm) were used to preparemesoporous electrodes for dye-sensitized solar cells. Electron transport in the solar cells was studied usingintensity-modulated photocurrent spectroscopy and revealed very similar results for ZnO and TiO2. Apparentactivation energies for electron transport in nanostructured ZnO of 
0.1 eV were calculated from thetemperature dependence of transport times under short-circuit conditions. The lifetime of electrons in thenanostructured semiconductors was evaluated from open-circuit voltage decay and intensity-modulatedphotovoltage spectroscopy. Significantly longer lifetimes were obtained with ZnO. Despite the reducedrecombination, ZnO-based solar cells performed worse than TiO2 cells, which was attributed to a lower electroninjection efficiency from excited dye molecules and/or a lower dye regeneration efficiency. The internalvoltage in the nanostructured ZnO film under short-circuit conditions was about 0.23 V lower than the open-circuit potential at the same light intensity. Results may be explained using a multiple trapping model, but aselectrons are usually only shallowly trapped in ZnO, an alternative view is presented. If there is significantdoping of the ZnO, resulting band bending in the nanocrystals will form energy barriers for electron transportand recombination that can explain the observed properties.
0.1 eV were calculated from thetemperature dependence of transport times under short-circuit conditions. The lifetime of electrons in thenanostructured semiconductors was evaluated from open-circuit voltage decay and intensity-modulatedphotovoltage spectroscopy. Significantly longer lifetimes were obtained with ZnO. Despite the reducedrecombination, ZnO-based solar cells performed worse than TiO2 cells, which was attributed to a lower electroninjection efficiency from excited dye molecules and/or a lower dye regeneration efficiency. The internalvoltage in the nanostructured ZnO film under short-circuit conditions was about 0.23 V lower than the open-circuit potential at the same light intensity. Results may be explained using a multiple trapping model, but aselectrons are usually only shallowly trapped in ZnO, an alternative view is presented. If there is significantdoping of the ZnO, resulting band bending in the nanocrystals will form energy barriers for electron transportand recombination that can explain the observed properties.