SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 36: Poster Session III: Electronic structure of surfaces: Spectroscopy, surface states I
O 36.4: Poster
Dienstag, 2. März 2021, 10:30–12:30, P
Importance of surface oxygen vacancies for ultrafast hot carrier relaxation and transport in Cu2O: Insight from hybrid DFT — •Chiara Ricca1, Lisa Grad2, Matthias Hengsberger2, Jürg Osterwalder2, and Ulrich Aschauer1 — 1Department of Chemistry and Biochemistry and National Centre for Computational Design and Discovery of Novel Materials MARVEL, University of Bern, CH-3012 Bern, Switzerland — 2Department of Physics, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
Efficient Cu2O-based electrodes for photochemical water splitting can be engineered through a deeper understanding of the surface defects and of the mechanisms responsible for the capture of the excited carriers that limit the generated photovoltage in Cu2O heterostructures. Using hybrid DFT calculations, we confirmed that the (√3×√3)-R30 reconstruction at the Cu2O-(111) surface is associated with a 1/3 monolayer of charged surface oxygen vacancies forming ordered structures due to mutual repulsion. Comparison with experimental data obtained by two-photon photoemission spectroscopy indicates that the defect states associated with these vacancies can strongly suppress electron transport, while bulk defect states cannot act as electron traps. In particular, the excited electronic state of the singly charged oxygen vacancy plays a crucial role in the non-radiative electron capture process, with capture coefficients of about 10-9 cm3/s and lifetimes of 0.04 ps, allowing to explain the experimentally observed ultrafast carrier relaxation.