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

• Published in: Inorganic chemistry Vol. 59; no. 23; pp. 17379 - 17384
• Main Authors: Yamamoto, Takafumi, Oswald, Iain W. H, Savory, Christopher N, Ohmi, Takuya, Koegel, Alexandra A, Scanlon, David O, Kageyama, Hiroshi, Neilson, James R
• Format: Journal Article
• Language: English
• Published: American Chemical Society 07-12-2020
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.0c02686

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)2PbI2–x Br 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.