Effect of Cu content on electrical properties of evaporated Cu-Se thermoelectric films

Abstract Cu-Se compounds have attracted extensive attention in the field of thermoelectric field, especially for the Cu-Se film material. Cu content will affect the conductivity and Seebeck coefficient of the Cu-Se films. Thus, the Cu-Se films with Cu contents in the range of 58%–90% are prepared by vacuum thermal evaporation to explore the effect of Cu contents on microstructure and electrical properties. The phase composition changes from CuSe phase to Cu2Se phase and then to the coexistence of Cu phase and Cu2Se phase with increasing the Cu contents. In various Cu contents, the Cu0.68Se0.32 film is mainly formed by β-Cu2Se phase and presents smooth and dense surface. This makes the film have lower resistivity and the highest Seebeck coefficient than the cases with other Cu contents. The film has maximum power factor of 770 μW m-1 K-2 at 250 °C when the atomic ratio of the film is close to 2:1.