First-Principles Investigation of Cubic Tin and Germanium Sulfides and Selenides for Photovoltaic and Thermoelectric Applications

Chalcogenide compound semiconductors offer a wide range of band gaps with many prospective applications in photovoltaics, near-infrared devices, and thermoelectrics. In this work, we investigate the electronic and optical properties of the recently synthesized, cubic polymorph π-tin sulfide, as well as the germanium and selenide analogs, with predictive calculations based on density functional and many-body perturbation theory. Structural relaxation calculations provide the equilibrium geometry and thermodynamic properties. The electronic structure is determined with the GW method and the optical absorption spectrum is obtained with the Bethe-Salpeter equation. Our calculations provide insights into the applications of cubic chalcogenides in the π structure for photovoltaic and thermoelectric applications.