Electron Transport in Acceptor-Sensitized Polymer鈥揙xide Solar Cells: The Importance of Surface Dipoles and Electron Cascade Effects
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- 作者：Seare A. Berhe ; Joy Y. Zhou ; Keith M. Haynes ; Marco T. Rodriguez ; W. Justin Youngblood
- 刊名：ACS Applied Materials & Interfaces
- 出版年：2012
- 出版时间：June 27, 2012
- 年：2012
- 卷：4
- 期：6
- 页码：2955-2963
- 全文大小：522K
- 年卷期：v.4,no.6(June 27, 2012)
- ISSN：1944-8252
文摘
Fullerene and acenequinone compounds have been examined as electron mediators between a p-type semiconductive polymer and two n-type oxide semiconductors. Composite interlayer materials and photovoltaic test cells were assembled and studied for their fluorescence quenching, current鈥搗oltage, and quantum efficiency behavior to characterize the efficacy of the acceptor-sensitizers as electron-selective interlayers. The sensitizers are generally more effective with titanium dioxide than with zinc oxide, due to the difference in magnitude of dipole-induced vacuum level shifts at the respective oxide interfaces. In titanium dioxide-based solar cells, where dipole effects are weak, photovoltage and fill factor increase in a trend that matches the increase in the first reduction potential of the acceptor-sensitizers. Photosensitization of the oxide semiconductor by the acceptor-sensitizers is observed to operate either in parallel with the polymer as an alternate photosensitizer or in series with the polymer in a two-photon process, according to an acceptor-sensitizer鈥檚 first reduction potential. In zinc oxide-based solar cells, where dipole effects are stronger, the acceptor-sensitizers impaired most devices, which is attributed to an upward shift of the oxide鈥檚 conduction band edge caused by dipole-induced vacuum level shifts. These results have broad implications for designing electron-selective interlayers and solid-state photocells using sensitized oxide semiconductors.