Enhancing thermoelectric performance via synergistic regulation of band structure and microstructure in Cu-doped WS2 polycrystalline films

Thermoelectric materials have great potential in the energy recovery and environmental protection, and thermoelectric films can also effectively achieve heat dissipation of the chip through thermoelectric refrigeration. WS2 films show good thermoelectric performance in prediction, but the figure of merit (ZT) of the synthesized WS2 films still needs improvement. In this work, Cu was doped into WS2 films by magnetron sputtering combined with chemical vapor deposition and sulfurization annealing. Cu doping narrowed the band gap and increased the hole concentration from 5.6 x 10(19) cm(-3) to 2.2 x 10(21) cm(-3), greatly improved the electrical properties of WS2 film. At 300 K, the electrical conductivity and power factor of Cu-doped films increased by 1086 % and 575 % compared to pristine WS2, respectively. In addition, Cu doping reduced the grain size and introduced more grain boundaries, which decreased the in-plane thermal conductivity to as low as 0.22 W m(-1) K-1 at 300 K. The coupling of the electrical and thermal properties optimization greatly improved ZT. The ZT value of Cu-5.5-WS2 films is as high as 0.181 at 425 K. This work provides a new idea for improving the thermoelectric performance of transition metal dichalcogenides (TMDCs) films.