Flexible 3D Porous MoS₂/CNTs Architectures with ZT of 0.17 at Room Temperature for Wearable Thermoelectric Applications

Abstract

Developing materials that possess high electrical conductivities (σ) and Seebeck coefficients (S), low thermal conductivities (κ), and excellent mechanical properties is important to realize practical thermoelectric (TE) devices. Here, 3D hierarchical architectures consisting of hybrid molybdenum disulfide (MoS2)/carbon nanotubes (CNTs) films are fabricated with the goal of increasing σ and decreasing κ. In these films, perpendicularly orientated CNTs interpenetrate restacked MoS2 layers to form a 3D architecture, which increases the specific surface area and charge concentration. The MoS2/20 wt% CNTs film shows high σ (235 ± 5 S∙cm−1), high S (68 ± 2 µV∙K−1), and low κ (19 ± 2 mW∙m−1∙K−1). The corresponding figure of merit (ZT) reaches 0.17 at room temperature, which is 65 times higher than that of pure MoS2 film. In addition, the MoS2/20 wt% CNTs film shows a tensile stress of 38.9 MPa, which is an order of magnitude higher than that of a control MoS2 film. Using the MoS2/CNTs film as an active material and human body as a heat source, a flexible, wearable TE wristband is fabricated by weaving seven strips of the 3D porous MoS2/CNTs film. The wristband achieves an output voltage of 2.9 mV and corresponding power output of 0.22 µW at a temperature gradient of about 5 K.

Flexible electronics based on 2D transition metal dichalcogenides

“…The decoration of CNTs onto MoS 2 thin lms can effectively increase the electrical conductivity and reduce the thermal conductivity. 301 CNTs also have an inuence on the shi of the Fermi level towards the valence band edge and increase the Seebeck coefficient. Hence, 20% doping of CNTs into MoS 2 resulted in a ZT of 0.17.…”

Flexible and wearable plasmonic-enabled organic/inorganic hybrid photothermoelectric generators

“…5 There were also flexible and wearable TE devices based on p/n Sb 2 Te 3 /Bi 2 Te 3 fabricated on silk 49 and uni-leg-type MoS 2 -CNTs fabricated on cotton. 17 But no sun light harvest has been reported on these devices built on silk or cotton. Considering the on-going developments obtained on ultra-low power electronic circuits 50,51 and the possibility to combine wearable electronics with the micro-electromechanical system (MEMS) technology, 52,53 the 14 current wearable photothermoelectric generators offer bright perspectives to harvest energy for multifunctional smart textiles.…”

“…by environment-induced temperature difference). 5,16,17 Concerning light harvesting, organic solar TE generators face similar challenges as inorganic TE counterparts to obtain sufficient temperature difference across the device under illumination. On classical inorganic TE modules, a few mitigation strategies have been proposed: For example, on Bi 2 Te 3 TE elements, commercial multilayer thin-film light absorbers have been applied to boost the temperature difference of the device under solar illumination.…”

Highly Flexible and Durable Thermoelectric Power Generator Using CNT/PDMS Foam by Rapid Solvent Evaporation

“…In these regards, several groups have reported porous TE materials with low thermal conductivities. [ 20–25 ] Wang et al. and Thongkham et al.…”

“…reported porous molybdenum disulfide/CNT composites with a thermal conductivity of 0.19 W m −1 K −1 using a freeze drying method. [ 23 ] Although these works demonstrated that a porous structure can enhance the TE performance by decreasing the thermal conductivity, the mechanical stability and durability of TE materials subject to external stress including tensile, compressive, and vibrational stress have rarely been reported. Importantly, owing to the weak mechanical strength of TE materials, the mechanical flexibility of TEGs has mainly relied on the presence of TE‐inactive elastomer‐based matrix or substrate.…”