Mixed valence Sn doped (CH3NH3)3Bi2Br9 produced by mechanochemical synthesis. Issue 6 (26th January 2023) - Jia, Xiaohan
Abstract : Mechanochemical synthesis leads to mixed valence Sn(ii )/Sn(iv ) doping of the triple vacancy ordered perovskite MA3 Bi2 Br9 . Abstract : Bismuth halides with formula A3 Bi2 X9, where A is an inorganic or organic cation, show desirable properties as solar absorbers and luminescent materials. Control of structural and electronic dimensionality of these compounds is important to yield materials with good light absorption and charge transport. Here we report mechanochemical reaction of (CH3 NH3 )3 Bi2 Br9 with SnBr2 at room temperature in air, yielding a material with strong absorption across the visible region. We attribute this to mixed valence doping of Sn(ii ) and Sn(iv ) on the Bi site. X-Ray diffraction shows no secondary phases, even after heating at 200 °C to improve crystallinity. X-Ray photoelectron spectroscopy suggests the presence of Sn(ii ) and Sn(iv ) states. A similar approach to dope Sn into the iodide analogue (CH3 NH3 )3 Bi2 I9 was unsuccessful.