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State Selective Dynamics of TiO2 Charge Carrier Trapping and Recombination

preprint
revised on 14.07.2019, 23:13 and posted on 15.07.2019, 16:56 by Yu Zhang, Daniel T. Payne, Chi L. Pang, Cephise Cacho, Richard T. Chapman, Emma Springate, Helen Fielding, Geoff Thornton

Time-resolved pump-probe photoemission spectroscopy has been used to study the dynamics of charge carrier recombination and trapping on hydroxylated rutile TiO2(110). Two types of pump excitation were employed, one in the infrared (0.95 eV) and the other in the UV (3.5 eV) region. With IR excitation, electrons associated with defects are excited into the bottom of the conduction band from the polaronic states within the band gap, which are retrapped within 45±10 fs. Under UV excitation, the electrons in these band gap states and valence band electrons are excited into the conduction band. In addition to the fast polaron trapping observed with IR excitation, we also observe a long lifetime (about 1 ps) component to both the depletion of hot electrons at the bottom of the conduction band and the refilling of the band gap states. This points to a band gap state mediated recombination process with a ps lifetime.

Funding

Advanced Grant ENERGYSURF (GT), EPSRC (UK) (EP/D068673/1), EU COST Action CM1104, and the Royal Society (UK) through a Wolfson Research Merit Award to GT

History

Email Address of Submitting Author

yu.zhang@stfc.ac.uk

Institution

Central laser facility, STFC, UKRI

Country

United Kingdom

ORCID For Submitting Author

0000-0001-6184-4870

Declaration of Conflict of Interest

The authors declare no competing financial interest.

Version Notes

Version 1.1

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in The Journal of Physical Chemistry Letters

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