First principles study of structural, electronic, optical and thermoelectric properties of Ag 3 XY 2 (X = Cu, Cd, Zn: Y -- Se, Te)

The investigation of the structural, electronic, optical and thermoelectric properties of Ag 3 XY 2 (X = Cu, Cd, Zn; Y -- Se, Te) with full potential linearized augmented plane wave (FP-LAPW) method has been carried. To get accurate bandgap values the modified Becke-Johnson (mBJ) exchange potential was applied. Two materials Ag 3 CuSe 2 and Ag 3 CuTe 2 have band gap values of 0.62 eV and 0.53 eV. TDOS plot of these materials gives the contribution of each element (Ag, Cu, Se/Te) in VBM and CBM. The optical properties found that Ag 3 CuTe 2 has higher optical conductivity than Ag 3 CuSe 2 and also has a high absorption coefficient. Thermoelectric properties were calculated and it is observed that the numerical value of Seebeck coefficient of Ag 3 CuSe 2 is higher than Ag 3 CuTe 2 at room temperature. But from the calculation of the figure of merit (ZT), we concluded that Ag 3 CuTe 2 has high value of ZT than Ag 3 CuSe 2 in both p -type and n -type regions. So, Ag 3 CuTe 2 can be used as the best thermoelectric material in both p -type and n -type as compared to Ag 3 CuSe 2 .