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HL: Fachverband Halbleiterphysik
HL 33: Nitrides I – Growth and fabrication
HL 33.5: Vortrag
Mittwoch, 11. März 2026, 17:30–17:45, POT/0006
Influence of A-Site Cations on Structure, Defect Density and Photoactivity of Tantalum-Based Perovskite Oxynitride Photoelectrodes — •Gabriel Grötzner1,2, Aleksandr Kochergov1,2, Oliver Brune1,2, Laura I. Wagner1,2, Saswati Santra1,2, Verena Streibel1,2, and Ian D. Sharp1,2 — 1Walter Schottky Institute, Technische Universität München, Germany — 2Physics Department, TUM School of Natural Sciences, Technische Universität München, Germany
Perovskite oxynitrides are emerging materials for photoelectrochemical (PEC) water splitting, yet the influence of the A-site cation on their material properties remains poorly understood. Here, we investigate a series of ATaON2 thin films (A = La, Ce, Pr, Nd, Gd, ordered by decreasing ionic radius) to elucidate the role of the A-site cation on structural, optoelectronic, and PEC properties. X-ray diffraction analysis reveals a systematic lattice contraction with decreasing ionic radius of the A-site cation. This structural change is accompanied by an increase in optical band gap from 1.8 eV to 2.2 eV and a reduction in sub-bandgap absorption, indicating lower defect densities for smaller A-site cations. Electrical measurements show reduced conductivity for GdTaON2 compared to LaTaON2, consistent with defect suppression. By changing the A-site cation from La to Gd, the photocurrent density in PEC measurements doubles, despite an increase in optical band gap, which indicates the beneficial impact of reduced defect-mediated recombination. These insights offer design principles for defect and band-structure engineering in perovskite oxynitride photoanodes.
Keywords: Thin Films; Oxynitrides; Perovskites; Photoelectrochemistry; Defects