Thermoelectric performance of copper-rich β-Cu2Se films with Ag-doping by magnetron sputtering

The concept of “phonon-liquid electron-crystal” (PLEC) have attracted many researchers for thermoelectric materials. In this study, a series of Ag-doped β-Cu2Se films were prepared on single crystalline Si(111) substrate by magnetron sputtering and the influence of Ag doping on the phase composition, chemical component and thermoelectric performance of the deposited β-Cu2Se films were studied. An energy dispersive spectrometer (EDS) showed that the Cu-rich β-Cu2Se films in which the ratio of Cu to Se in β-Cu2Se lattice varied from 3.59 to 4.96 as Ag atomic percent content increased from 0 to 2.97 were obtained. The Ag existed in the form of CuAgSe phase which increased electrical resistivity and Seebeck coefficient. The phase transition from α to β phase of Cu2Se only took place at ~60 °C. The variation of electrical resistivity with Ag content relied on the combined action of the amounts of CuAgSe phase and the ratio of Cu to Se in β-Cu2Se lattice of deposited films. The power factor of 1.37 at% Ag samples at whole measured temperature was the highest in all samples due to high Seebeck coefficient. It was attributed to lower resistivity than that of bulk Ag-doped β-Cu2Se materials of references that the power factor of our deposited films reached the order of mW.m−1K−2.