Anharmonicity and Octahedral Tilting in Hybrid Vacancy-Ordered Double Perovskites
[1];
[2];
[1]
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom, Thomas Young Centre, University College London, Gower Street, London WC1E 6BT, United Kingdom, Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
The advantageous performance of hybrid organic–inorganic perovskite halide semiconductors in optoelectronic applications motivates studies of their fundamental crystal chemistry. In particular, recent studies have sought to understand how dipolar, dynamic, and organic cations such as methylammonium (CH3NH3+) and formamidinium (CH(NH2)2+) affect physical properties such as light absorption and charge transport. To probe the influence of organic–inorganic coupling on charge transport, we prepared the series of vacancy-ordered double perovskite derivatives A2SnI6, where A = Cs+, CH3NH3+, and CH(NH2)2+. Despite nearly identical cubic structures by powder X-ray diffraction, replacement of Cs+ with CH3NH3+ or CH(NH2)2+ reduces conductivity through a reduction in both carrier concentration and carrier mobility. We attribute the trends in electronic behavior to anharmonic lattice dynamics from the formation of hydrogen bonds that yield coupled organic–inorganic dynamics. This anharmonicity manifests as asymmetry of the interoctahedral I–I pair correlations in the X-ray pair distribution function of the hybrid compounds, which can be modeled by large atomistic ensembles with random rotations of rigid [SnI6] octahedral units. The presence of soft, anharmonic lattice dynamics holds implications for electron–phonon interactions, as supported by calculation of electron–phonon coupling strength that indicates the formation of more tightly bound polarons and reduced electron mobilities with increasing cation size. By exploiting the relatively decoupled nature of the octahedral units in these defect-ordered perovskite variants, we interrogated the impact of organic–inorganic coupling and lattice anharmonicity on the charge transport behavior of hybrid perovskite halide semiconductors.
- Research Organization:
- Colorado State Univ., Fort Collins, CO (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Contributing Organization:
- Advanced Photon Source; ARCHER UK National Supercomputing Service; EPSRC Centre for Doctoral Training in Molecular Modeling and Materials Science
- Grant/Contract Number:
- SC0016083; AC02-06CH11357
- OSTI ID:
- 1414778
- Alternate ID(s):
- OSTI ID: 1410796; OSTI ID: 1508269
- Journal Information:
- Chemistry of Materials, Journal Name: Chemistry of Materials Vol. 30 Journal Issue: 2; ISSN 0897-4756
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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