Regensburg 2019 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 15: Energy materials (other than photovoltaics)
HL 15.2: Vortrag
Dienstag, 2. April 2019, 09:45–10:00, H33
The roles of polarons and defects in charge carrier transport in BiVO4 photoanodes for solar water splitting — •Viktoria Kunzelmann, Irina Ilicheva, Alex Henning, and Ian Sharp — Walter Schottky Institute and Physics Department, Technical University of Munich, Garching, Germany
Hydrogen generation by solar water splitting provides a promising route towards the sustainable storage of solar energy. Bismuth vanadate (BiVO4) has a favorable band gap (2.5 eV) for solar light absorption and it has been demonstrated as a photoanode in photoelectrochemical cells (PEC) with one of the highest solar-to-hydrogen conversion efficiencies using metal oxide electrodes. While it is known that polarons and defects in BiVO4 limit electron and hole mobilities, and thereby the PEC efficiency, their energetics and influence on macroscopic cell parameters have not yet been determined. This work aims to identify the energy levels of polarons and defects and to understand their effects on the surface photovoltage. Temperature-dependent photocurrent spectroscopy and photothermal deflection spectroscopy are used to investigate interband absorption, self-trapping and localization of carriers as well as their escape mechanisms in polycrystalline BiVO4 thin films. These measurements yield key ensemble-averaged physical insights that are complemented with the nanoscale spatial characterization of surface photovoltage and charge transport by Kelvin probe force microscopy and conductive AFM, respectively.