Bond Valences and Anharmonicity in Vacancy-Ordered Double Perovskite Halides
- Colorado State Univ., Fort Collins, CO (United States). Department of Chemistry
We report that anharmonic lattice dynamics are intimately linked with optical and electronic properties in perovskite halides semiconductors. Vacancy-ordered double perovskites are a subset of the perovskite halide family containing isolated octahedral units. The absence of polyhedral connectivity engenders the vacancy-ordered double perovskites with additional degrees of dynamic freedom, which presents an ideal structural framework to study dynamic-property relationships in perovskite halide semiconductors. In the present study, we examine the structure and bonding origins of anharmonicity in the vacancy-ordered double perovskites Cs2Sn1-xTexI6. While X-ray diffraction indicates that all members adopt the cubic vacancy-ordered double perovskite structure, the local coordination environment probed by X-ray pair distribution function (XPDF) analysis reveals asymmetry of the Cs–I/I–I pair correlation that smoothly decreases with increasing tellurium content. Temperature-dependent neutron total scattering suggests that this asymmetry in the PDF occurs due to anharmonic lattice dynamics arising from octahedral tilting and Cs+ displacements, as supported by Reverse Monte Carlo simulations of the Cs2SnI6 and Cs2TeI6 end members. We further correlate the trends in asymmetry and anharmonicity with the bond valence sum of the Cs+ ion, and find that the anharmonicity vanishes when the bonding preferences of the Cs+ are satisfied by the size of the cuboctahedral void. Lastly, this study presents a simple and effective approach for understanding the origin of anharmonicity in vacancy-ordered double perovskite materials.
- Research Organization:
- Colorado State Univ., Fort Collins, CO (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC0016083; AC02-06CH11357
- OSTI ID:
- 1478240
- Alternate ID(s):
- OSTI ID: 1479127
- Journal Information:
- Journal of Materials Chemistry C, Vol. 6, Issue 44; ISSN 2050-7526
- Publisher:
- Royal Society of ChemistryCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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