Structure and Optical Properties of Layered Perovskite (MA)2PbI2- xBrx(SCN)2 (0 ≤ x < 1.6)

Takafumi Yamamoto; Iain W H Oswald; Christopher N Savory; Takuya Ohmi; Alexandra A Koegel; David O Scanlon; Hiroshi Kageyama; James R Neilson

doi:10.1021/acs.inorgchem.0c02686

Structure and Optical Properties of Layered Perovskite (MA)₂PbI_{2- x}Br_x(SCN)₂ (0 ≤ x < 1.6)

Inorg Chem. 2020 Dec 7;59(23):17379-17384. doi: 10.1021/acs.inorgchem.0c02686. Epub 2020 Nov 24.

Authors

Takafumi Yamamoto^{1

2}, Iain W H Oswald³, Christopher N Savory^{4

5}, Takuya Ohmi¹, Alexandra A Koegel³, David O Scanlon^{4

5

6}, Hiroshi Kageyama^{2

7}, James R Neilson³

Affiliations

¹ Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama 226-8503, Japan.
² Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
³ Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States.
⁴ Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, United Kingdom.
⁵ Thomas Young Centre, University College London, Gower Street, London WC1E 6BT, United Kingdom.
⁶ Diamond Light Source Ltd., Diamond House, Didcot, Oxfordshire OX11 0DE, United Kingdom.
⁷ CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan.

PMID: 33232604
DOI: 10.1021/acs.inorgchem.0c02686

Abstract

The layered perovskite (MA)₂PbI₂(SCN)₂ (MA = CH₃NH₃⁺) is a member of an emerging series of compounds derived from hybrid organic-inorganic perovskites. Here, we successfully synthesized (MA)₂PbI_2-xBr_x(SCN)₂ (0 ≤ x < 1.6) by using a solid-state reaction. Despite smaller bromide substitution for iodine, 1% linear expansion along the a axis was observed at x ∼ 0.4 due to a change of the orientation of the SCN^- anions. Diffuse reflectance spectra reveal that the optical band gap increases by the bromide substitution, which is supported by the DFT calculations. Curiously, bromine-rich compounds where x ≥ 0.8 are light sensitive, leading to partial decomposition after ∼24 h. This study demonstrates that the layered perovskite (MA)₂PbI₂(SCN)₂ tolerates a wide range of bromide substitution toward tuning the band gap energy.