Long-Lived Photoexcited Carrier Dynamics of d–d Excitations in Spinel Ordered Co3O4

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• 作者：Matthias M. Waegele ; Hoang Q. Doan ; Tanja Cuk
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：February 20, 2014
• 年：2014
• 卷：118
• 期：7
• 页码：3426-3432
• 全文大小：333K
• ISSN：1932-7455

文摘

The spectrum and dynamics of excited carriers in a spinel-ordered transition metal oxide, Co₃O₄, were investigated by both selective photoexcitation of all major optical transitions and selectively filling electronic states through an applied voltage. Co₃O₄ contains strong absorptions at all relevant optical excitations common to transition-metal oxides, inclusive of ligand-to-metal charge transfer, metal-to-metal charge transfer, and intravalence d鈥?/i>d transitions. We find that carriers initially excited across the charge-transfer excitations quickly (3 ps) convert to d鈥?/i>d excitations due to strong electron鈥損honon coupling. Subsequent recombination from weakly coupled, localized excited d states to the ground state occurs at a much longer, nanosecond time scale. These results suggest that d鈥?/i>d excitations represent a special type of long-lived recombination center intrinsic to a transition-metal oxide. Such carrier dynamics may apply to a wider range of transition metal oxides actively being integrated in photocatalytic and photovoltaic devices.