- Matthias M. Waegele,听Hoang Q. Doan, and听Tanja Cuk*
- J. Phys. Chem. C,听2014,听118听(7), pp 3426鈥�3432听DOI:听10.1021/jp4113443.听Download
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听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�d transitions. We find that carriers initially excited across the charge-transfer excitations quickly (鈭�3 ps) convert to d鈥�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�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.
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