Synthesis and characterisation of Cu2ZnSnSe4 thin films prepared via a vacuum evaporation-based route

Different sequentially stacked binary chalcogenide layers (CuSe, ZnSe, and SnSe) deposited by vacuum evaporation onto molybdenum covered soda-lime glass substrates were used as precursors to form Cu2ZnSnSe4 films. The influence of the stacked binary layer sequence, substrate temperature, both the duration and speed of deposition and the post deposition treatment atmosphere on the structural and the morphological parameters of the Cu2ZnSnSe4 thin films was studied. Our results indicate the possibility of replacing the Se2 selenisation with a thermal treatment in an SnSe2 atmosphere to avoid the selenisation of the Mo substrate and MoSe2 formation. This SnSe2 treatment forms p-type Cu2ZnSnSe4 films with an optical band-gap of 1.14 eV and a solar cell structure with an efficiency of up to 3%.

► Cu2ZnSnSe4 thin films were grown using binary precursors and selenisation. ► Composition and morphology were studied in dependence of selenisation atmosphere. ► The use of SnSe2 selenisation allows to avoid Mo substrate selenisation. ► The high quality of films is indicated by the value of their Eg = 1.14 eV. ► Cu2ZnSnSe4 thin films were in p-type conductivity and were realized as solar cells.