Optimization of MoSe 2 formation for Cu(In,Ga)Se 2 -based solar cells by using thin superficial molybdenum oxide barrier layers

Abstract During the formation of Cu(In,Ga)Se 2 thin films deposited on Mo substrate by the selenization of Cu-In-Ga precursor, the reaction of Mo with Se can lead to a high consumption of Mo back contact and the formation of a thick MoSe 2 layer, thus deteriorating the electrical properties of the back contact. In this study, the effect of thermal oxidation pre-treatment on Mo has been investigated to control the growth of MoSe 2 . It has been demonstrated that a thin and covering MoO 2 layer can block the selenization of Mo. Using this effect, a MoSe 2 layer with controlled thickness can be formed by adding a thin and controlled Mo layer on top of an oxidized Mo substrate. In this configuration, only the Mo added on top of oxidized Mo forms MoSe 2 and the whole Mo protected by MoO 2 remains after selenization. Thanks to this Glass/Mo/MoO 2 /Mo substrate configuration and the metallic behavior of MoO 2 , the good electrical properties of the back contact are kept after selenization.