Jump to main content
Jump to site search


Operando electrochemical study of charge carrier processes in water splitting photoanodes protected by atomic layer deposited TiO2

Author affiliations

Abstract

Semiconductor-based solar energy conversion devices are often multilayer structures with each layer serving a distinct purpose towards generating an efficient and stable device. In water splitting, the use of atomic layer deposited TiO2 (ALD-TiO2) layers enables the stable operation of materials that would normally photocorrode in the aqueous electrolyte. Interestingly, thick ALD-TiO2 (>50 nm) has been successfully used to protect high performance photoanodes, despite an apparent band mismatch that should preclude charge transfer. The understanding of the charge transfer through the relatively thick TiO2 layer remains controversial and warrants further study. Here, we introduce an operando methodology to study charge carrier processes in the ALD-TiO2 protected photoanode by utilizing photoelectrochemical impedance spectroscopy (PEIS) combined with the dual-working-electrode (DWE) technique to resolve if the charge transport through the TiO2 is a conduction band process or involves a hopping through defect states. Two silicon-based systems were evaluated, one featuring a buried homojunction (np+Si/TiO2/Ni) and the other a purely n-type Si directly interfaced with TiO2 (nSi/TiO2/Ni). The additional series resistance imparted by the TiO2 layer (RTiO2) was extracted from the PEIS measurements. Both the potential and thickness dependence of RTiO2 were analyzed, and the DWE technique enabled the sensing of the potential of the TiO2 layer under operation, indicating a strong band bending with the conduction band even more positive than the oxygen evolution potential. Together, these data suggest a conduction band-based transport mechanism, in spite of the presence of defect states in the bandgap of ALD-TiO2, and a detailed picture of the charge transfer through the multilayer structured photoanodes was obtained.

Graphical abstract: Operando electrochemical study of charge carrier processes in water splitting photoanodes protected by atomic layer deposited TiO2

Back to tab navigation

Supplementary files

Publication details

The article was received on 25 Jun 2019, accepted on 28 Aug 2019 and first published on 03 Sep 2019


Article type: Paper
DOI: 10.1039/C9SE00399A
Sustainable Energy Fuels, 2019, Advance Article
  • Open access: Creative Commons BY license
  •   Request permissions

    Operando electrochemical study of charge carrier processes in water splitting photoanodes protected by atomic layer deposited TiO2

    W. Cui, T. Moehl, S. Siol and S. D. Tilley, Sustainable Energy Fuels, 2019, Advance Article , DOI: 10.1039/C9SE00399A

    This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Material from this article can be used in other publications provided that the correct acknowledgement is given with the reproduced material.

    Reproduced material should be attributed as follows:

    • For reproduction of material from NJC:
      [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the Centre National de la Recherche Scientifique (CNRS) and the RSC.
    • For reproduction of material from PCCP:
      [Original citation] - Published by the PCCP Owner Societies.
    • For reproduction of material from PPS:
      [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology, the European Photochemistry Association, and RSC.
    • For reproduction of material from all other RSC journals:
      [Original citation] - Published by The Royal Society of Chemistry.

    Information about reproducing material from RSC articles with different licences is available on our Permission Requests page.

Search articles by author

Spotlight

Advertisements