Bubeck, Cora ; Widenmeyer, Marc ; De Denko, Alexandra T. ; Richter, Gunther ; Coduri, Mauro ; Colera, Eduardo Salas ; Goering, Eberhard ; Zhang, Hongbin ; Yoon, Songhak ; Osterloh, Frank E. ; Weidenkaff, Anke (2020)
Bandgap-adjustment and enhanced surface photovoltage in Y-substituted LaTaIVO2N.
In: Journal of Materials Chemistry A, 8 (23)
doi: 10.1039/D0TA02136A
Artikel, Bibliographie
Kurzbeschreibung (Abstract)
Perovskite-type oxynitrides AB(O,N)3 are photocatalysts for overall water splitting under visible light illumination. In the past, structurally labile perovskite-type oxynitrides (e.g. YTaON2) were predicted to be highly suitable. In this work, we tackle the challenging YTa(O,N)3 synthesis by Y-substitution in LaTaIVO2N resulting in phase-pure La0.9Y0.1TaIVO2N, La0.75Y0.25TaIVO2N, and La0.7Y0.3TaIVO2N. By using microcrystalline YTaO4 together with an unconventional ammonolysis protocol we synthesized the highest reported weight fraction (82(2) wt%) of perovskite-type YTa(O,N)3. Ta4+ in La1−xYxTaIVO2N was verified by X-ray photoelectron spectroscopy (XPS) and X-ray near edge absorption structure (XANES) analysis. Density functional theory (DFT) calculations revealed a transparent conductor-like behavior explaining the unusual red/orange color of the Ta4+-containing perovskites. In combination with crystal structure analysis the DFT calculations identified orthorhombic strain as the main descriptor for the unexpected trend of the optical bandgap (EG,x=0.3 ≈ EG,x=0 < EG,x=0.1 < EG,x=0.25). Surface photovoltage spectroscopy (SPS) of particulate La1−xYxTaIVO2N (x = 0, 0.1, 0.25, 0.3) films revealed negative photovoltages at photon energies exceeding 1.75 eV, confirming that these materials are n-type semiconductors with effective bandgaps of ∼1.75 eV irrespective of the Y content. The photovoltage values increased with the Y content, suggesting an improved carrier generation and separation in the materials. However, increasing the Y content also slowed down the timescales for photovoltage generation/decay indicating trap states in the materials. Based on our results, we suggest a significantly weaker as classically assumed impact of reduced B-site metal cations such as Ta4+ on the photovoltage and charge carrier recombination rate.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2020 |
| Autor(en): | Bubeck, Cora ; Widenmeyer, Marc ; De Denko, Alexandra T. ; Richter, Gunther ; Coduri, Mauro ; Colera, Eduardo Salas ; Goering, Eberhard ; Zhang, Hongbin ; Yoon, Songhak ; Osterloh, Frank E. ; Weidenkaff, Anke |
| Art des Eintrags: | Bibliographie |
| Titel: | Bandgap-adjustment and enhanced surface photovoltage in Y-substituted LaTaIVO2N |
| Sprache: | Englisch |
| Publikationsjahr: | 19 Mai 2020 |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Journal of Materials Chemistry A |
| Jahrgang/Volume einer Zeitschrift: | 8 |
| (Heft-)Nummer: | 23 |
| DOI: | 10.1039/D0TA02136A |
| URL / URN: | https://doi.org/10.1039/D0TA02136A |
| Kurzbeschreibung (Abstract): | Perovskite-type oxynitrides AB(O,N)3 are photocatalysts for overall water splitting under visible light illumination. In the past, structurally labile perovskite-type oxynitrides (e.g. YTaON2) were predicted to be highly suitable. In this work, we tackle the challenging YTa(O,N)3 synthesis by Y-substitution in LaTaIVO2N resulting in phase-pure La0.9Y0.1TaIVO2N, La0.75Y0.25TaIVO2N, and La0.7Y0.3TaIVO2N. By using microcrystalline YTaO4 together with an unconventional ammonolysis protocol we synthesized the highest reported weight fraction (82(2) wt%) of perovskite-type YTa(O,N)3. Ta4+ in La1−xYxTaIVO2N was verified by X-ray photoelectron spectroscopy (XPS) and X-ray near edge absorption structure (XANES) analysis. Density functional theory (DFT) calculations revealed a transparent conductor-like behavior explaining the unusual red/orange color of the Ta4+-containing perovskites. In combination with crystal structure analysis the DFT calculations identified orthorhombic strain as the main descriptor for the unexpected trend of the optical bandgap (EG,x=0.3 ≈ EG,x=0 < EG,x=0.1 < EG,x=0.25). Surface photovoltage spectroscopy (SPS) of particulate La1−xYxTaIVO2N (x = 0, 0.1, 0.25, 0.3) films revealed negative photovoltages at photon energies exceeding 1.75 eV, confirming that these materials are n-type semiconductors with effective bandgaps of ∼1.75 eV irrespective of the Y content. The photovoltage values increased with the Y content, suggesting an improved carrier generation and separation in the materials. However, increasing the Y content also slowed down the timescales for photovoltage generation/decay indicating trap states in the materials. Based on our results, we suggest a significantly weaker as classically assumed impact of reduced B-site metal cations such as Ta4+ on the photovoltage and charge carrier recombination rate. |
| Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Theorie magnetischer Materialien 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Werkstofftechnik und Ressourcenmanagement |
| Hinterlegungsdatum: | 17 Jun 2020 07:18 |
| Letzte Änderung: | 13 Jan 2024 18:25 |
| PPN: | |
| Projekte: | The authors acknowledge the financial support and granted radiation beam time of the European Synchrotron Radiation Facility, Grenoble, France and Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany., This work was supported by the Deutsche Forschungsgemeinschaft within the priority program SPP 1613 “Solar H2” (WE 2803/7-1)., Support for surface photovoltage spectroscopy measurements was provided by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Grant DOE-SC0015329. |
| Export: | |
| Suche nach Titel in: | TUfind oder in Google |
 |
Frage zum Eintrag |
Optionen (nur für Redakteure)
 |
Redaktionelle Details anzeigen |
Drucken
Impressum