This title appears in the Scientific Report :
2020
Please use the identifier:
http://dx.doi.org/10.1515/zpch-2019-1481 in citations.
Stability and Degradation Mechanism of Si-based Photocathodes for Water Splitting with Ultrathin TiO2 Protection Layer
Stability and Degradation Mechanism of Si-based Photocathodes for Water Splitting with Ultrathin TiO2 Protection Layer
Using transmission and scanning electron microscopy, we study mechanisms which determine the stability of Silicon photocathodes for solar driven water splitting. Such tandem or triple devices can show a promising stability as photocathodes if the semiconductor surface is protected by an ultrathin Ti...
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Personal Name(s): | Ronge, Emanuel |
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Cottre, Thorsten / Welter, Katharina / Smirnov, Vladimir / Ottinger, Natalie Jacqueline / Finger, Friedhelm / Kaiser, Bernhard / Jaegermann, Wolfram / Jooss, Christian (Corresponding author) | |
Contributing Institute: |
Photovoltaik; IEK-5 |
Published in: | Zeitschrift für physikalische Chemie, 234 (2020) 6, S. 1171–1184 |
Imprint: |
Berlin
De Gruyter
2020
|
DOI: |
10.1515/zpch-2019-1481 |
Document Type: |
Journal Article |
Research Program: |
Solar cells of the next generation |
Publikationsportal JuSER |
Using transmission and scanning electron microscopy, we study mechanisms which determine the stability of Silicon photocathodes for solar driven water splitting. Such tandem or triple devices can show a promising stability as photocathodes if the semiconductor surface is protected by an ultrathin TiO2 protection layer. Using atomic layer deposition (ALD) with Cl-precursors, 4–7 nm thick TiO2 layers can be grown with high structural perfection. The layer can be electrochemically covered by Pt nanoparticels serving as electro-catalysts. However, Cl-remnants which are typically present in such layers due to incomplete oxidation, are the origin of an electrochemical degradation process. After 1 h AM1.5G illumination in alkaline media, circular shaped corrosion craters appear in the topmost Si layer, although the TiO2 layer is intact in most parts of the crater. The crater development is stopped at local inhomogenities with a higher Pt coverage. The observations suggests that reduced Titanium species due to Cl−/O2− substitution are nucleation sites of the initial corrosion steps due to enhanced solubility of reduced Ti in the electrolyte. This process is followed by electrochemical dissolution of Si, after direct contact between the electrolyte and the top Si layer surface. To increase the stability of TiO2 protected photocathodes, formation of reduced Ti species must be avoided. |