Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 51: Functional Semiconductors for Renewable Energy Solutions II

HL 51.5: Talk

Friday, March 22, 2024, 10:30–10:45, ER 325

Emerging oxynitride photoelectrodes for stable and efficient energy conversion — •Tobias Haubold — Walter-Schottky-Institute, Technische Universität München, Germany

Photoelectrochemical solar water splitting represents a promising approach for the direct conversion of visible light into chemical fuels. To overcome the efficiency and stability limitations of pure oxide and nitride photosystems, respectively, high-throughput computational screening has identified oxynitrides as an interesting material space that offers narrower bandgaps and improved charge carrier mobility. While several studies have reported the synthesis of oxynitrides and demonstrated their application for photoelectrochemical energy conversion, controlled synthesis routes for high-quality materials and a fundamental understanding of semiconductor and defect-related properties are still lacking. Here, we leverage reactive magnetron sputtering and subsequent annealing as a controllable synthesis platform to deposit tantalum oxynitride thin films with controlled structure, chemical composition, and optoelectronic quality. By variation of the N2-O2 process gas mixture, we were able to systematically study the impact of anion non-stoichiometry on optical properties and photoelectrochemical performance. The gained insights will reveal the impact of electronically active oxygen- and nitrogen-related defect states within the bandgap on the semiconductor properties of oxynitrides.

Keywords: oxynitrides; sputtering; Energy conversion; Hydrogen; Photoelectrochemical solar water splitting