Modulating the optoelectronic and thermoelectric properties of chalcopyrite AgXTe2 (X: Ga, In) via in-plane biaxial strain

The influence of biaxial-in-plan strain on optoelectronic and thermoelectric characteristics of AgXTe2 (X: Ga, In) chalcopyrite type compound has been investigated using density function theory base on full potential linear augmented plane wave technique. The generalized Perdew-Burke-Ernzerhof gradient approximation (PBEsol GGA) is used to optimize unit cell and the Tran-Blaha modified Becke-Johnson (TB-mBJ) approach is employed to improve the electronic, optical and thermoelectric properties. The effects of biaxial strains of the tensile (1%, 2%, 3%) and compression (-1%, -2%, -3%) have been calculated along with contribution of two cations (Ga and In). The calculated band gap of AgGaTe2 and AgInTe2 without strain is 1.17 and 1.13 eV that decreases with applied tensile strain and increases with compressive strain. Without strain maximum absorption is obtained at 1.3 eV and 1.1 eV AgGaTe2 and AgInTe2 respectively, however, tensile and compressive strain shows red and blue shift accordingly. The increase in flatness of valance band with compressive strain results in a large Seebeck coefficient due the large hole effective mass. This identifies AgGaTe2 as a possible efficient thermoelectric material. Consequently, the present study is very useful for developments of desired characteristics by applying strain for optoelectronic and thermoelectric devices.