First principle study of structural, electronic, optical and electric properties of Ag2ZnGeX4(S, Se)

Equilibrium Stannite structure (SS), Kesterite structure (KS) and Diamond structure of Ag2MnSnS4 are investigated by using density functional theory (DFT) within Wien2k code based on the generalized gradient approximation (GGA) and the modified Becke-Johnson exchange potential (mBJ). P-type conductivity is found for Kesterite and Stannite phases while n-type semiconductor is found for Diamond phase. For all structures, Ag2MnSnS4 exhibits a semiconductor characteristic with a direct band gap of 1.24 eV,1.4eV and 1.7eV for Stannite, Kesterite and diamond structure respectively. Additionally, the calculations of the electronic and optical properties of the compounds display a considerable wavelength absorption in the ultraviolet range. Furthermore, the findings obtained for Ag2MnSnS4 have later been subjected to a comparative study, whereby the theoretical and experimental results of Cu2ZnSnS4 (CZTS) belonging to the same chalcogenide family, have been adopted.