Ab-initio investigations for structural, optoelectronic and thermoelectric properties of Li2BeXSe4 (X = Ge, Si, Sn) compounds

Abstract

Motivated by photovoltaic activities, we study certain aspects of the stannite structure (ST) of the Li2BeXSe4 (X = Ge, Si, Sn) compounds using the full potential augmented plane wave approach implemented in the Wien2k code. Concretely, we use the generalized gradient approximation (GGA) and the modified Becke–Johnson exchange potential (mBJ) to evaluate in a precise way, the band gaps, the total and the partial densities, as well as the optical and the thermoelectric properties. Among others, we show that the Li2BeXSe4 (X = Ge, Si, Sn) semiconductors exhibit a direct band gap in the Γ point of the Brillouin Zone (BZ). Furthermore, the optical properties of the three compounds show a strong optical conductivity and a good optical absorption. As a result, we reveal that the proposed materials are suitable for the application in photovoltaic solar cells. Using the BoltzTrap package, we also examine and discuss the thermoelectric properties such as the Seebeck coefficient (S), the electrical conductivity, and the thermal conductivity as a function of the temperature. We find that the Li2BeXSe4 (X = Ge, Si, Sn) compounds exhibit good thermoelectric transport properties, making them a good candidates for clean energy applications.