Tuning the thermoelectric properties of ZnO/MoS₂/carbon fabric via interface-induced energy filtering effect for wearable thermoelectric application

Wearable thermoelectric generators, capable of converting human body heat into electricity are one of the most suitable forms of power source to fabricate self-powered wearable electronic devices. Molybdenum disulfide (MoS₂), owing to its large intrinsic bandgap and high carrier mobility is one of the most widely explored materials for thermoelectric application. In this work, 2D MoS₂ nanosheets were grown on the conductive carbon fabric (CF) by a binder-free in situ hydrothermal method and the 3D ZnO nanoparticles were decorated on them via a facile dip coating technique, to form a 3D/2D interface. Apart from providing a flexible substrate to the material, the CF aids the MoS₂ with higher carrier concentration and mobility. Thus, the pristine MoS₂ possesses the highest electrical conductivity (σ) of all the samples at 373 K. The 20-mg ZnO-decorated sample achieved a maximum Seebeck coefficient (S) of 11.7 μV/K at 373 K, which is 1.25 times higher than that of pristine MoS₂/CF. This enhancement in S is ascribed to the higher energy filtering effect at the ZnO/MoS₂ interface that allows the flow of only high-energy carriers. The 15-mg ZnO-decorated sample with optimum S and σ had the highest power factor (PF) of 311 nW/mK² at 373 K which is 1.2 times higher than that of the pristine sample. This enhancement in PF is mainly due to the synergistic effect of large σ and an extremely low activation energy of 0.00802 eV. Thus, the optimum concentration of ZnO nanoparticles for an enhanced PF is 15 mg owing to its very low activation energy.