Synthesis, optical band gap and thermoelectric properties of Sr1+xTiS3-y chalcogenide perovskites

Inorganic chalcogenide perovskites are semiconductors with attractive optoelectronic properties, which make them of interest in different fields, such as energy harvesting. Some of these compounds have been poorly investigated to date. For instance, very few works deal with the synthesis and characterization of Sr1+xTiS3. Here we present a novel synthesis procedure to obtain Sr1+xTiS3-y powders. Moreover, we show for the first time an experimental characterization of some fundamental properties of this compound that may be relevant for many potential applications. First, we demonstrate that this perovskite shows very high thermal stability (up to 700°C in air and up to 1200°C in Ar atmosphere). Next, we experimentally determine its optical band gap (about 0.97 eV) corresponding to a direct allowed transition, in agreement with previous predictions. Finally, we demonstrate a tuneable Seebeck coefficient (changing from n-type to p-type behaviour) by changing the amount of sulfur vacancies.