The mechanical and optoelectronic properties of (Cu1-xAgx)2ZnSnSe4 solid solutions: A theoretical study

Abstract

A theoretical investigation of the structural, mechanical, electronic, and optical properties of (Cu1-xAgx)2SnZnSe4 (CAZTSe) solid solutions has been performed. The kesterite-type structure is more stable than the stannite-type structure for A2ZnSnX4 (A = Cu, Ag; X = S, Se) at room temperature. The tendency for phase segregation is greatly reduced for CAZTSe solid solutions with increasing the concentration of Ag doping. The mechanical stability and the nature of ductility are found for each compound. The results show that the electronic properties are calculated well by the PBE0 functional. The bowing band gap observed from experiments could be explained from the existence of the metastable structure. The band gap is increased by increasing the concentration of Ag doping. The optical properties are greatly affected by Ag doping. The light absorption capacity is reduced from 400 to 800 nm, while the absorption coefficient is slightly improved between 300 and 400 nm.