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Anatase TiO2 is a superior material for converting light into other forms of energies. Despite the extensive studies of its photophysics, only recently the importance of e-h interactions in TiO2 was understood [1]. Here, we apply a novel ultrafast broadband deep-UV spectroscopy setup to access for the first time the nonequilibrium dynamics of TiO2 at the band edge. By monitoring the evolution of exciton nonlinearities, we reveal an ultrafast electron cooling in the conduction band [2], and demonstrate a novel methodology to probe selectively the interfacial charge injection from a dye to TiO2 [3].
[1] E. Baldini, L. Chiodo, A. Dominguez, M. Palummo, S. Moser, M. Yazdi-Rizi, G. Auböck, B. P. P. Mallett, H. Berger, A. Magrez, C. Bernhard, M. Grioni, A. Rubio, and M. Chergui, “Strongly Bound Excitons in Anatase TiO2 Single Crystals and Nanoparticles”, Nat. Comm. 8, 13 (2017).
[2] E. Baldini, T. Palmieri, E. Pomarico, G. Auböck, and M. Chergui, “Clocking the Ultrafast Electron Cooling in Anatase Titanium Dioxide Nanoparticles”, ACS Photonics, DOI: 10.1021/acsphotonics.7b00945 (2018).
[3] E. Baldini, T. Palmieri, T. Rossi, M. Oppermann, E. Pomarico, G. Auböck, and M. Chergui, “Ultrafast Interfacial Electron Injection Probed by a Substrate-Specific Excitonic Signature”, J. Amer. Chem. Soc. 139, 11584-11589 (2017).
