Enhancement of the thermoelectric properties in β-Cu2+xSe/a-C nano-multilayer films by heterogeneous interfaces

The β-Cu2+xSe/a-C nano-multilayer films were prepared. The carrier concentration, mobility and thermal conductivity decrease and the resistivity and Seebeck coefficient increase with reducing the modulation periods. For the β-Cu2+xSe/a-C nano-multilayer film with the lowest modulation period 160 nm, the power factor and ZT value reach 0.57 mW·m−1·K−2 and 0.42 at room temperature, respectively. Enhanced power factor and ZT values in the nano-multilayer films are attributed to scattering effect of the depletion layer at the β-Cu2+xSe/a-C interface that decreases the carrier concentration and mobility. The existence of the heterogeneous interface effectively increases the Seebeck coefficient and decreases thermal conductivity due to increasing the scattering effect of carriers and phonons. The introduction of a-C layer with high electric conduction into β-Cu2+xSe to form β-Cu2+xSe/a-C nano-multilayer film can effectively improve its thermoelectric properties.