A density functional theory study (GGA+U) of the electronic and optical properties of Sn doped acanthite Cu₂S

Cu₂S is earth abundant, non-toxic and an important semiconductor with many applications. Previously it sought wide attention to scientific community as a promising photovoltaic material since Cu₂S based thin film solar cells demonstrated nearly 10% conversion efficiency. Despite excessive Cu vacancy formation tendency, studies on Cu₂S based thin film solar cells didn’t lose its importance in decades. Our recently published theoretical study (J. Phys.: Condens. Matter 30 165701) on the acanthite phase of Cu₂S showed that Cu vacancy formation tendency can be reduced with Ag alloying. Hence, alloying with other materials needs to be studied systematically, as well. Here, we report a systematic first principle study on Sn doped acanthite Cu₂S. We have showed that Sn doping in this structure is even thermodynamically more favorable. Even though excessive Sn doping makes the material metallic, the Cu vacancy formation tendency decreases with high doping concentration. With suitable low doping the material undergoes electronic intraband transition which extends the optical absorption to the infrared region. In addition, detail electronic structures and optical properties will be presented for pure and Sn doped cases.