Flexible n-type thermoelectric materials by organic intercalation of layered transition metal dichalcogenide TiS2

Organic semiconductors are attracting increasing interest as flexible thermoelectric materials owing to material abundance, easy processing and low thermal conductivity. Although progress in p-type polymers and composites has been reported, their n-type counterpart has fallen behind owing to difficulties in n-type doping of organic semiconductors. Here, we present an approach to synthesize n-type flexible thermoelectric materials through a facile electrochemical intercalation method, fabricating a hybrid superlattice of alternating inorganic TiS 2 monolayers and organic cations. Electrons were externally injected into the inorganic layers and then stabilized by organic cations, providing n-type carriers for current and energy transport. An electrical conductivity of 790 S cm −1 and a power factor of 0.45 mW m −1 K −2 were obtained for a hybrid superlattice of TiS 2 /[(hexylammonium) x (H 2 O) y (DMSO) z ], with an in-plane lattice thermal conductivity of 0.12 ± 0.03 W m −1 K −1 , which is two orders of magnitude smaller than the thermal conductivities of the single-layer and bulk TiS 2 . High power factor and low thermal conductivity contributed to a thermoelectric figure of merit, ZT , of 0.28 at 373 K, which might find application in wearable electronics. A flexible n-type material has been developed with a thermoelectric figure of merit of 0.28 at 373 K via the intercalation of organic cations between titanium disulphide monolayers.