α-Cu2Se thermoelectric thin films prepared by copper sputtering into selenium precursor layers

Copper selenide (Cu2Se) is a promising thermoelectric material and alpha-phase Cu2Se provides relatively safe thermoelectric modules for thin film thermoelectric device in contrast to some toxic materials currently on the market. In this work, nanocrystalline Cu2Se thin film with uniform element distribution was fabricated at room temperature through an effective combination reaction method by implanting sputtered Cu+ ions into Se precursor. Then, self-assembled growth of Cu2Se thin films with desired alpha-phase and well crystallinity was successfully achieved with optimization of annealing temperature. Interestingly, the growth orientation has obviously affected by the annealing temperature, which significantly affects the thermoelectric properties. Consequently, the Seebeck coefficients increase with the increase in the orientation factor of the (0l0) preferred orientation, which enhances power factor. The high maximum power factor of 9.23 mu Wcm(-1) K-2 is achieved for alpha-Cu2Se thin film with (0l0) preferred orientation, demonstrating that the method used in this work has great potential in developing low-cost and high-performance thermoelectric thin films from relatively earth-abundant elements.