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Title: Tolerance Factor and Cooperative Tilting Effects in Vacancy-Ordered Double Perovskite Halides

Journal Article · · Chemistry of Materials
ORCiD logo [1];  [2];  [1]; ORCiD logo [2]; ORCiD logo [1]
  1. Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States
  2. Kathleen Lonsdale Materials Chemistry, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom, Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom, Thomas Young Centre, University College London, Gower Street, London WC1E 6BT, United Kingdom
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Lattice dynamics and structural instabilities are strongly implicated in dictating the electronic properties of perovskite halide semiconductors. We present a study of the vacancy-ordered double perovskite Rb2SnI6 and correlate dynamic and cooperative octahedral tilting with changes in electronic behavior compared to those of Cs2SnI6. Though both compounds exhibit native n-type semiconductivity, Rb2SnI6 exhibits carrier mobilities that are reduced by a factor of ~50 relative to Cs2SnI6. From synchrotron powder X-ray diffraction, we find that Rb2SnI6 adopts the tetragonal vacancy-ordered double perovskite structure at room temperature and undergoes a phase transition to a lower-symmetry monoclinic structure upon cooling, characterized by cooperative octahedral tilting of the [SnI6] octahedra. X-ray and neutron pair distribution function analyses reveal that the local coordination environment of Rb2SnI6 is consistent with the monoclinic structure at all temperatures; we attribute this observation to dynamic octahedral rotations that become frozen in to yield the low-temperature monoclinic structure. In contrast, Cs2SnI6 adopts the cubic vacancy-ordered double perovskite structure at all temperatures. Density functional calculations show that static octahedral tilting in Rb2SnI6 results in marginally increased carrier effective masses, which alone are insufficient to account for the experimental electronic behavior. Rather, the larger number of low-frequency phonons introduced by the lower symmetry of the Rb2SnI6 structure yield stronger electron–phonon coupling interactions that produce larger electron effective masses and reduced carrier mobilities relative to Cs2SnI6. Further, we discuss the results for Rb2SnI6 in the context of other vacancy-ordered double perovskite semiconductors, in order to demonstrate that the electron–phonon coupling characteristics can be predicted using the geometric perovskite tolerance factor. This study represents an important step in designing perovskite halide semiconductors with desired charge transport properties for optoelectronic applications.

Research Organization:
Colorado State Univ., Fort Collins, CO (United States); Univ. College London (United Kingdom)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES); Engineering and Physical Sciences Research Council (EPSRC)
Grant/Contract Number:
AC02-06CH11357; SC0016083; EP/L000202; EP/N01572X/1; EP/L015862/1
OSTI ID:
1457590
Alternate ID(s):
OSTI ID: 1499116
Journal Information:
Chemistry of Materials, Journal Name: Chemistry of Materials Vol. 30 Journal Issue: 11; ISSN 0897-4756
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 70 works
Citation information provided by
Web of Science

Cited By (12)

Two-dimensional lead-free iodide-based hybrid double perovskites: crystal growth, thin-film preparation and photocurrent responses journal January 2019
Spectrally Tunable and Stable Electroluminescence Enabled by Rubidium Doping of CsPbBr 3 Nanocrystals journal September 2019
Progress of Lead‐Free Halide Double Perovskites journal January 2019
Tin Halide Perovskite (ASnX 3 ) Solar Cells: A Comprehensive Guide toward the Highest Power Conversion Efficiency journal September 2019
Mechanochemical Synthesis of Sn(II) and Sn(IV) Iodide Perovskites and Study of Their Structural, Chemical, Thermal, Optical, and Electrical Properties journal April 2020
The Role of Goldschmidt’s Tolerance Factor in the Formation of A 2 BX 6 Double Halide Perovskites and its Optimal Range journal July 2019
Structurally Stabilizing and Environment Friendly Triggers: Double‐Metallic Lead‐Free Perovskites journal May 2019
The chemical forces underlying octahedral tilting in halide perovskites journal January 2018
Bond valences and anharmonicity in vacancy-ordered double perovskite halides journal January 2018
Computational prediction of structural, electronic, and optical properties and phase stability of double perovskites K 2 SnX 6 (X = I, Br, Cl) journal January 2020
Advances in modelling and simulation of halide perovskites for solar cell applications journal January 2019
Ordering of hidden multipoles in spin-orbit entangled 5 d 1 Ta chlorides journal July 2019

Figures / Tables (16)

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Figure 11(p. 9)figure Figure 11

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