TiO 2-SnO 2:F interfacial electronic structure investigated by soft x-ray absorption spectroscopy

Coleman X. Kronawitter, Mukes Kapilashrami, Jonathan R. Bakke, Stacey F. Bent, Cheng Hao Chuang, Way Faung Pong, Jinghua Guo, Lionel Vayssieres, Samuel S. Mao

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Abstract

The electronic structure of the titanium dioxide (TiO 2)- fluorine-doped tin dioxide (SnO 2:F) interface is investigated by soft x-ray absorption spectroscopy using synchrotron radiation. The measurements probe the site- and symmetry-selected unoccupied density of states and reflect the interaction between an early transition-metal-oxide (d0) semiconductor and a post-transition-metal-oxide (d10) degenerate semiconductor. The distinct interfacial electronic structure of TiO 2-SnO 2:F is established by contrasting spectra with those for anatase and rutile TiO 2, SnO 2:F, and ZnO-SnO 2:F and CdO-SnO 2:F interfaces. Oxygen 1s absorption spectra, which relate to the O 2p partial density of states of the conduction band, indicate that the interface is associated with a reduction in Ti d-O p orbital hybridization and an alteration of the TiO 2 crystal field. These observations are consistent with measured titanium 2p absorption spectra, which in addition provide evidence for distortion of long-range order around the cation site in the interfacial TiO 2. The TiO 2-SnO 2:F interface is a functional component of a number of optoelectronic devices, perhaps most notably within the anode structure of solar cell architectures. In nonequilibrium conditions, such as those found in operating solar cells, interfacial electronic structure directly influences performance by modifying, for instance, the quasi-Fermi level electrons and the potential distribution at the transparent electrode.

Original languageBritish English
Article number125109
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume85
Issue number12
DOIs
StatePublished - 9 Mar 2012

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