Berlin 2018 – scientific programme

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DS: Fachverband Dünne Schichten

DS 6: Thin Film Applications

DS 6.7: Talk

Monday, March 12, 2018, 16:45–17:00, H 0111

Bottom-up Synthesis and Characterization of Mesoporous Al-Modified Hematite Thin Film Photo-Anodes — •Ahmed Chnani and Steffen Strehle — Ulm University, Institute of Electron Devices and Circuits, Albert-Einstein-Allee 45, 89081 Ulm

Hematite (α-Fe2O3) is an earth abundant, low-cost and non-toxic n-type semiconductor being in the research focus for the assembly of efficient photo-anodes in the field of solar fuel production by water splitting. Despite a suitable band structure and sufficient water splitting stability, there are various critical issues that need to be resolved including for instance the short charge carrier lifetime that is significantly misaligned with the optical absorption length, an overall low electrical conductivity as well as a low surface charge transfer kinetics.

In this paper, aluminium is added to hematite as a sustainable strategy to reduce the defect state density while simultaneously increasing the charge carrier concentration. For the studies, thermally evaporated Fe(Al) thin films with roughly 200 nm in thickness were utilized. By rational control of a plain thermal oxidation process under ambient conditions, non-porous to mesoporous Al-modified hematite thin films were prepared. The experiments show that mesoporous thin films show not only efficient light trapping but also an overall increased electrical conductivity and an increased photoactivity in comparison to non-porous thin films, plain hematite electrodes and even in comparison to high-density hematite nanowire arrays. The complete surface band structure was reconstructed to evaluate the surface defect states by utilizing a Kelvin probe as well as ambient photoelectron spectroscopy.