Carrier Localization on the Nanometer-Scale limits Transport in Metal Oxide Photoabsorbers

Markus Schleuning, Moritz Kölbach, Ibbi Ahmet, Raphael Präg, Ronen Gottesman, René Gunder, Mengyuan Zhang, Dan Ralf Wargulski, Daniel Abou-Ras, Daniel A. Grave, Fatwa F. Abdi, Roel van de Krol, Klaus Schwarzburg, Rainer Eichberger, Dennis Friedrich*, Hannes Hempel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Metal oxides are considered as stable and low-cost photoelectrode candidates for hydrogen production by photoelectrochemical solar water splitting. However, their power conversion efficiencies usually suffer from poor transport of photogenerated charge carriers, which has been attributed previously to a variety of effects occurring on different time and length scales. In search for common understanding and for a better photo-conducting metal oxide photoabsorber, CuFeO2, α-SnWO4, BaSnO3, FeVO4, CuBi2O4, α-Fe2O3, and BiVO4 are compared. Their kinetics of thermalization, trapping, localization, and recombination are monitored continuously 100 fs–100 µs and mobilities are determined for different probing lengths by combined time-resolved terahertz and microwave spectroscopy. As common issue, we find small mobilities < 3 cm2V-1s-1. Partial carrier localization further slows carrier diffusion beyond localization lengths of 1–6 nm and explains the extraordinarily long conductivity tails, which should not be taken as a sign of long diffusion lengths. For CuFeO2, the localization is attributed to electrostatic barriers that enclose the crystallographic domains. The most promising novel material is BaSnO3, which exhibits the highest mobility after reducing carrier localization by annealing in H2. Such overcoming of carrier localization should be an objective of future efforts to enhance charge transport in metal oxides.

Original languageAmerican English
Article number2300065
JournalAdvanced Functional Materials
Issue number25
StatePublished - 19 Jun 2023

Bibliographical note

Publisher Copyright:
© 2023 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.


  • carrier localization
  • metal oxides
  • mobilities
  • photoconductivity
  • water splitting


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