Mechanochemical Synthesis of Sn(II) and Sn(IV) Iodide Perovskites and Study of Their Structural, Chemical, Thermal, Optical, and Electrical Properties

Phase-pure CsSnI3, FASnI(3), Cs(PbSn)I-3, FA(PbSn)I-3 perovskites (FA = formamidinium = HC(NH2)(2)(+)) as well as the analogous so-called vacancy-ordered double perovskites Cs2SnI6 and FA(2)SnI(6) are mechanochemically synthesized. The addition of SnF2 is found to be crucial for the synthesis of Cs-containing perovskites but unnecessary for hybrid ones. All compounds show an absorption onset in the near-infrared (NIR) region, which makes them especially relevant for photovoltaic applications. The addition of Pb(II) and SnF2 is crucial to improve the electronic properties in 3D Sn(II)-based perovskites, in particular their charge carriers mobility (approximate to 0.2 cm(2) Vs(-1)) which is enhanced upon reduction of the dark carrier conductivity. Stokes-shifted photoluminescence is observed on dry powders of Sn(II)-based perovskites, which makes these materials promising for light-emitting and sensing applications. Thermal stability of all compounds is examined, revealing no significant degradation up to at least 200 degrees C. This meets the requirements for standard operation conditions of most optoelectronic devices and is potentially compatible with thermal vacuum deposition of polycrystalline thin films.