Improving the thermoelectric performance of Cu-doped MoS₂ film by band structure modification and microstructural regulation

Two-dimensional (2D) layered transitional metal dichalcogenides (TMDCs) semiconductors like MoS₂ have been predicted to be promising thermoelectric (TE) materials due to their high carrier mobility. However, the TE performance of MoS₂ film is severely hindered by the high in-plane thermal conductivity. In this work, based on reversing grain orientation reducing in-plane thermal conductivity, Cu doping is used to increase the carrier concentration for optimization of electrical properties. The Cu-doped MoS₂ films have prepared by magnetron sputtering (MS) combined with post-sulfurization chemical vapor deposition (CVD). The composition, structure, thermal and electrical properties were systematically investigated by experiment and DFT calculation. Results indicate that Cu doping may slightly reduce the Seebeck coefficient of MoS₂ film, but effectively narrow the band gap and improve the carrier concentration, thus improving the electrical performance. In addition, MS combined with CVD method can effectively increase the degree of grain misorientation, making the in-plane thermal conductivity of Cu-doped MoS₂ film much lower. Combined with the above optimization, a promising maximum ZT value among TMDCs 0.137 at 425 K was obtained in Cu₆-MoS₂ film. This study provides a new strategy to synchronously regulate the thermal and electrical properties of TMDCs films to improve their thermoelectric performances.