Capturing transiently charged states at the C60/TiO2(110) interface by time-resolved soft X-ray photoelectron spectroscopy |
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| Affiliation: | 1. Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8551, Japan;2. Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan;3. Department of Physics, Sophia University, Chiyoda-ku, Tokyo 102-8554, Japan;1. Giresun University, Faculty of Engineering, Energy Systems Engineering, 28200, Giresun, Turkey;2. Giresun University, Faculty of Engineering, Environmental Engineering, 28200, Giresun, Turkey;3. Gazi University, Faculty of Arts and Sciences, Physics Department, 06500 Ankara, Turkey;1. Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing 100081, PR China;2. State Key Lab of Transducer Technology, Chinese Academy of Sciences, PR China;3. Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, PR China |
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| Abstract: | Time-resolved soft X-ray photoelectron spectroscopy is utilized to determine an energy level alignment and the photoexcited carrier dynamics at a C60/TiO2(110) interface. The interface electronic structure is characterized by a type II junction, which favors an injection of photoexcited electrons from C60 to TiO2. Ultraviolet (UV) laser pulse irradiation induces transient shifts of both C 1s and Ti 2p core levels towards the higher binding energies. These energy shifts are caused by a laser-induced charge transfer between the C60 layer and the TiO2(110) surface. Upon UV absorption, valence electrons of C60 are promoted to unoccupied levels, followed by a resonant transfer to TiO2, leaving C60 in a cationized state. On the TiO2(110) side, the electrons are injected into the conduction band to raise the carrier density so that downward bending of the TiO2 band is induced. The UV-excited states of C60 and TiO2 have sufficiently longer lifetime than the lifetime of the electron–hole pairs in solid C60. The C60/TiO2(110) interface is, thus, proved to be efficient for separating the electron–hole pairs generated within the C60 layer. |
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| Keywords: | Time-resolved measurements Soft X-ray photoelectron spectroscopy Carrier dynamics Fullerene Dye sensitized solar cell |
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