Preparation of Cu2Se thin films by vacuum evaporation and hot-pressing

A method using vacuum evaporation and hot-pressing to prepare Cu2Se thin films on Cu substrates is developed. The effects of the heating temperature, heating time, and pressure on the crystallinities of the Cu2Se thin films were studied. The structure, morphology, and composition properties of the Cu2Se thin films were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results showed that the crystallinities of the Cu2Se thin films improved as the heating temperature was increased from 200 °C to 280 °C. A low pressure of 2 MPa and a short time of 5 min were sufficient to obtain highly crystalline Cu2Se thin films at 280 °C. The fabricated Cu2Se/Cu structure could directly convert heat to electricity with a thermoelectric potential of 12.6 mV at 400 K and 17.8 mV at 500 K. Compared with conventional hot-pressing of bulk materials, this method requires lower temperatures and smaller pressures.