Chemical Welding on Semimetallic TiS₂ Nanosheets for High-Performance Flexible n-Type Thermoelectric Films

Abstract

Solution-based processing of two-dimensional (2D) materials provides the possibility of allowing these materials to be incorporated into large-area thin films, which can translate the interesting fundamental properties of 2D materials into available devices. Here, we report for the first time a novel chemical-welding method to achieve high-performance flexible n-type thermoelectric films using 2D semimetallic TiS nanosheets. We employ chemically exfoliated TiS nanosheets bridged with multivalent cationic metal Al to cross-link the nearby sheets during the film deposition process. We find that such a treatment can greatly enhance the stability of the film and can improve the power factor by simultaneously increasing the Seebeck coefficient and electrical conductivity. The resulting TiS nanosheet-based flexible film shows a room temperature power factor of ∼216.7 μW m K, which is among the highest chemically exfoliated 2D transition-metal dichalcogenide nanosheet-based films and comparable to the best flexible n-type thermoelectric films, to our knowledge, indicating its potential applications in wearable electronics.

Recent Progress of Two-Dimensional Thermoelectric Materials

“…TiS 2 is another widely studied 2D thermoelectric materials [13,[183][184][185][186]. As shown in Fig.…”

“…g Seebeck coefficient, h electrical conductivity, and i power factor of the TiS 2 nanosheet assembled thin film. Reproduced with permission from Ref [183]…”

Design, Performance, and Application of Thermoelectric Nanogenerators

“…Most inorganic TE materials generally have the properties of brittleness, breakability, and high requirements for the preparation process, but they are still widely used by researchers due to relatively excellent TE properties. In recent years, 2D layered TE materials have gradually become burgeoning and popular, such as Te, graphene, TiS 2 , WS 2 nanomaterials, and other 2D nanomaterials with excellent photoelectric or thermoelectric performances. Compared with inorganic materials, some organic materials have not only superior electrical conductivity, but also excellent TE properties, such as PEDOT and its composites .…”

Temperature‐induced phonon behavior in titanium disulfide (TiS2) nanosheets

“…Titanium disulfide (TiS 2 ) belongs to the TMDC family and is a semimetal with small indirect band gap that can be opened and tuned via oxidation, stoichiometry modifications (e.g., Ti 1.023 S 2 ), or defects . The TiS 2 thin layers attract attention due to variety of possible applications, including thermoelectric devices, biosensors, energy storage, solar cells and may constitute a useful material for lithium‐ion battery production . In order to further explore the possibilities of TiS 2 applications in above‐mentioned examples, one needs to fully understand the fundamental properties of this material, including phonon properties.…”