Investigation of Mg dopant in Cu2SnSe3 thin films for photovoltaic applications

Mg-doped Cu2SnSe3 films were prepared by DC magnetron co-sputtering at room temperature for 1 h with two different targets of Cu and Sn or Cu-Mg and Sn based upon the formula of (Cu2−xMgx)SnSe3 at x = 0, 0.1, 0.2, and 0.3, abbreviated as Mg-x-Cu2SnSe3, or the [Mg]/([Cu]+[Mg]) composition ratios in the Cu-Mg target at 0, 0.05, 0.1, and 0.15, followed by a selenization procedure at 550 °C under the Se atmosphere. Mg-doped Cu2SnSe3 films were a cubic structure. The direct optical band gaps of Mg-x-CTSe films at x = 0, 0.1, 0.2, and 0.3 were estimated to be 1.19 eV, 1.18 eV, 1.19 eV, and 1.21 eV, respectively. Defect chemistry was studied by measuring structural and electrical properties of Mg-doped Cu2SnSe3 as a function of dopant concentration. Mg-x-CTSe films showed p-type at x = 0 and 0.1 and n-type at x = 0.2 and 0.3. The explanation based upon the Mg-to-Cu antisite donor defect for the change in electrical property was declared. Mg doping in controlling the electrical properties of CTSe films is fulfilled, as we did for its bulks.