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

Phase-pure CsSnI, FASnI, Cs(PbSn)I, FA(PbSn)I perovskites (FA = formamidinium = HC(NH)) as well as the analogous so-called vacancy-ordered double perovskites CsSnI and FASnI are mechanochemically synthesized. The addition of SnF 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 SnF is crucial to improve the electronic properties in 3D Sn(II)-based perovskites, in particular their charge carriers mobility (≈0.2 cm Vs) 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 °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.