Berlin 2024 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 16: Functional Semiconductors for Renewable Energy Solutions I
HL 16.4: Talk
Tuesday, March 19, 2024, 10:15–10:30, ER 325
Effects of Defects on the Optoelectronic Properties of Ta3N5 Thin Films — •Lukas M. Wolz1,2, Gabriel Grötzner1,2, Laura I. Wagner1,2, Tim Rieth1,2, Matthias Kuhl1,2, Guanda Zhou1,2, Verena Streibel1,2, Saswati Santra1,2, Ian D. Sharp1,2, and Johanna Eichhorn1,2 — 1Walter Schottky Institute, Technische Universität München — 2Physics Department, TUM School of Natural Sciences, Technische Universität München
Photoelectrochemical (PEC) energy conversion is a promising approach for efficient solar-to-fuel conversion. In this context, transition metal nitride semiconductors have recently emerged as an interesting class of materials for overcoming the limitations associated with commonly studied metal oxides. While the impact of oxygen impurities (ON) and nitrogen vacancies (vN) on the PEC activity has already been explored, the understanding of how these defects impact stability is still lacking. Here, we utilize a controllable synthesis approach to independently tune ON and vN concentrations in Ta3N5 and systematically investigate structural, compositional, optoelectronic, and PEC properties to establish the relationship between atomic-scale defects and macroscale PEC stability. Low oxygen concentrations facilitate the formation of deep vN defects, leading to charge recombination and limiting the PEC stability. Increasing oxygen incorporation leads to the passivation of vN defects, resulting in reduced defect absorption, improved charge separation, and enhanced material stability. Overall, these results show the detrimental role of vN and the beneficial impact of ON on the stability of Ta3N5.
Keywords: Photoinduced water splitting; Stability; Defects; Energy conversion; Deep level traps