Construction of an MXene/Organic Superlattice for Flexible Thermoelectric Energy Conversion

Construction of an inorganic/organic superlattice-based film has been proven effective in enhancing thermoelectric (TE) performance as well as flexibility by a variety of mechanisms, typically for two-dimensional (2D) TiS2-based flexible TEs. MXenes, typically, Ti3C2Tx, are a type of 2D material widely investigated in fields of flexible batteries and electromagnetic shielding, among others. However, they have rarely been reported in flexible TEs. One of the key factors is that the surface termination groups (−T) on an MXene could trap electrons, restricting the electronic transport. Herein, −T groups were tailored and substituted by organic ions (−HA) by facile preannealing, exfoliation, and reassembly. The intercalation of −HA introduced Ti–N bonding, forming a flexible MXene/organic superlattice film. The electrical conductivity of the superlattice film was increased by 5 times to 1.6 × 105 S m–1 due to defect reduction as well as the electron injection effect. While the Seebeck coefficient was maintained, the power factor was increased from 4 to 18 μW m–1 K–2. The TE module based on the superlattice film revealed an output power of 7.6 nW at a temperature gap of 50 K. This work opens up an avenue of fabricating flexible MXene-based TE films by tailoring the surface termination group and constructing inorganic/organic superlattice structures.