Cation distribution in Cu2ZnSnSe4, Cu2FeSnS4 and Cu2ZnSiSe4 by multiple-edge anomalous diffraction
Daniel M Többens1, Galina Gurieva1, Sara Niedenzu1
1Structure and Dynamics of Energy Materials, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, Berlin, 14165, Germany.
Summary
Multiple-Edge Anomalous Diffraction (MEAD) precisely mapped cation distribution in photovoltaic semiconductors. This technique revealed a highly ordered wurtz-kesterite structure in Cu2ZnSiSe4, challenging previous findings.
Area of Science:
- Materials Science
- Solid-State Physics
- Crystallography
Background:
- Quaternary sulfosalts, particularly adamantine compounds, are promising for photovoltaic applications.
- Cation order-disorder significantly impacts semiconductor properties, but distinguishing similar cations (Cu+, Zn2+, Fe2+) is challenging with standard X-ray diffraction.
- Understanding cation distribution is crucial for optimizing material performance.
Purpose of the Study:
- To apply Multiple-Edge Anomalous Diffraction (MEAD) for precise cation distribution analysis in quaternary sulfosalts.
- To investigate the cation order-disorder in materials like Cu2ZnSnSe4 (CZTSe), Cu2FeSnS4 (CFTS), and Cu2ZnSiSe4 (CZSiSe).
- To validate and refine existing structural models for these promising semiconductor materials.
Main Methods:
- Utilized Multiple-Edge Anomalous Diffraction (MEAD) by tracking individual Bragg peaks over element-specific absorption edges.
- Employed synchrotron radiation at Beamline KMC-2 (BESSY II) with upgraded MEAD capabilities.
- Complemented MEAD data with Anomalous X-ray powder diffraction and X-ray Absorption Fine Structure (XAFS) spectroscopy.
Main Results:
- Confirmed established cation distributions in Cu2ZnSnSe4 (CZTSe) and Cu2FeSnS4 (CFTS).
- Revealed a highly ordered wurtz-kesterite structure type for Cu2ZnSiSe4 (CZSiSe), contradicting prior literature.
- Demonstrated the effectiveness of MEAD in resolving cation ordering in complex semiconductor structures.
Conclusions:
- MEAD is a powerful technique for accurate cation distribution analysis in complex semiconductor materials.
- The findings for CZSiSe necessitate a revision of its structural model and understanding.
- Precise structural characterization is key to advancing photovoltaic material development.
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