Structure And Optical Properties Of Layered Perovskite (Ma)(2)Pbi2-Xbrx(Scn)(2) (0 <= X < 1.6)

The layered perovskite (MA)(2)PbI2(SCN)(2) (MA = CH3NH3+) is a member of an emerging series of compounds derived from hybrid organic-inorganic perovskites. Here, we successfully synthesized (MA)(2)PbI2-xBrx(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 similar to 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 similar to 24 h. This study demonstrates that the layered perovskite (MA)(2)PbI2(SCN)(2) tolerates a wide range of bromide substitution toward tuning the band gap energy.