Ab initio study of the electronic and structural properties of CsSnI3 perovskite

The CsSnI3 crystal belongs to an interesting class of semiconducting perovskite which is currently used in thin-film field-effect transistor made of organics-inorganics hybrid compounds. The benefit of using hybrid compounds resides in their ability to combine the advantage of these two classes of compounds: the high mobility of inorganic materials and the ease of processing of organic materials. In spite of the growing attention of this new material, very little is known about the electronic and structural properties of the inorganic part of this compounds. The CsSnI3 is known to adopt 3 crystalline phases depending on the temperature: cubic (a-phase, T-alpha >426K), tetragonal (beta-phase, 351K < T-beta less than or equal to 426K) and orthorhombic (gamma-phase, T-gamma less than or equal to 351K). We have calculated the electronic properties for these 3 phases within the frame work of density functional theory where a generalized gradient approximation was used to represent the exchange and correlation energy of the electrons. The calculations of the band structures show an increase of the band gap as the symmetry of the structure is reduced from the alpha to gamma phases. All the calculations were carry out using the Abinit code and details of these calculations will be presented.