Effects of Electron Trapping and Protonation on the Efficiency of Water-Splitting Dye-Sensitized Solar Cells

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• 作者：John R. Swierk ; Nicholas S. McCool ; Timothy P. Saunders ; Greg D. Barber ; Thomas E. Mallouk
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：August 6, 2014
• 年：2014
• 卷：136
• 期：31
• 页码：10974-10982
• 全文大小：449K
• ISSN：1520-5126

文摘

Water-splitting dye-sensitized photoelectrochemical (WS-DSPECs) cells employ molecular sensitizers to absorb light and transport holes across the TiO₂ surface to colloidal or molecular water oxidation catalysts. As hole diffusion occurs along the surface, electrons are transported through the mesoporous TiO₂ film. In this paper we report the effects of electron trapping and protonation in the TiO₂ film on the dynamics of electron and hole transport in WS-DSPECs. When the sensitizer bis(2,2鈥?bipyridine)(4,4鈥?diphosphonato-2,2鈥?bipyridine)ruthenium(II) is adsorbed from aqueous acid instead of from ethanol, there is more rapid hole transfer between photo-oxidized sensitizer molecules that are adsorbed from strong acid. However, the photocurrent and open-circuit photovoltage are dramatically lower with sensitizers adsorbed from acid because intercalated protons charge-compensate electron traps in the TiO₂ film. Kinetic modeling of the photocurrent shows that electron trapping is responsible for the rapid electrode polarization that is observed in all WS-DSPECs. Electrochemical impedance spectroscopy suggests that proton intercalation also plays an important role in the slow degradation of WS-DSPECs, which generate protons at the anode as water is oxidized to oxygen.