Fine-grained polycrystalline MoTe2 with enhanced thermoelectric properties through iodine doping

Consisting of heavy elements and favorable electronic structure, MoTe2 has great potential as a good thermoelectric material for heat-to-electricity conversion. While some experimental work has been performed on the p-type version, n-type MoTe2 is theoretically predicted to have a great conversion efficiency and is crucial for eventual device functionality, yet has not been explored. Here, the preparation and thermoelectric properties of n-type iodine-doped nano-polycrystalline MoTe2 are currently reported. Nano-polycrystalline MoTe2-xIx is obtained by ball milling and spark plasma sintering techniques. The composition, morphology and crystal structure of the prepared materials were analyzed by XRD and FESEM, which indicated a homogeneous single phase. The measured transport properties over the temperature range of 298-823 K indicate that iodine doping greatly enhances the carrier concentration and corresponding power factor, and drastically reducing the thermal conductivity. The ECR (Electrical conductivity ratios) carrier scattering analysis demonstrates that dislocation scattering is the main mechanism throughout the experimental temperature range. With the temperature and doping increasing, the thermal conductivity was reduced rapidly, and the minimum value was 1.19 Wm(-1) K-1 at 673 K. The maximum value of the figure merit ZT similar to 0.16 over 673-750 K, which is much higher than other reported values. These excellent properties imply that MoTe2 will be an efficient candidate for thermoelectric applications.

Automated summary

This study reports the preparation and thermoelectric properties of iodine-doped n-type nano-polycrystalline MoTe2, which showed significantly enhanced carrier concentration and power factor, and reduced thermal conductivity. The research also revealed that dislocation scattering is the main mechanism, with thermal conductivity rapidly decreasing with increasing temperature and doping.