Title: Measurement of the space-charge region width in BiVO4 particle films with surface photovoltage spectroscopy
Authors: Brett Hodges, Rachel Doughty, Anna Kundmann, and Frank E. Osterloh
Abstract: The use of semiconducting materials, such as bismuth vanadate (BiVO4), as nanoparticulate catalysts for photocatalytic water-splitting depends on the nature of electronic-band bending phenomena at the semiconductor-liquid interface. Electric fields present at this interface reduce the concentration of majority charge carriers within a region of the semiconductor, creating what is commonly referred to as a depletion/space-charge region. Currently, a model based on bulk semiconductors is used to measure the width of this space-charge region and relate it to electronic properties of the system, such as charge carrier density and interface voltage. However, it is unknown if this model accurately describes the space-charge region in nanoparticle systems. In this study, we utilize surface photovoltage spectroscopy (SPS) to probe the width of the space-charge region in BiVO4 particle films. Photoactive monoclinic-scheelite BiVO4 particles with an optical bandgap of 2.5eV were produced via a liquid-assisted solid-state synthesis. Films were prepared by drop-coating a BiVO4 solution onto gold-coated glass substrates and subsequently annealed. Characterization with surface profilometry and UV-Vis spectroscopy was conducted. Based on previous findings made by our group for strontium titanate particle films, we predict that space-charge region widths observed with SPS will be orders of magnitude larger than those predicted using the existing model. The current status of SPS characterization is to be discussed.