Robustly Enhanced Seebeck Coefficient in the MXene/Organics/TiS₂ Misfit Structure for Flexible Thermoelectrics

The flexible thermoelectric (TE) generator has emerged as a superior alternative to traditional batteries for powering wearable electronic devices, as it can efficiently convert skin heat into electricity without any safety concerns. MXene, a highly researched two-dimensional material, is known for its exceptional flexibility, hydrophilicity, metallic conductivity, and processability, among other properties, making it a versatile material for a wide range of applications, including supercapacitors, electromagnetic shielding, and sensors. However, the low intrinsic Seebeck coefficient of MXene due to its metallic conducting nature poses a significant challenge to its TE application. Therefore, improving the Seebeck coefficient remains a primary concern. In this regard, a flexible MXene/organics/TiS₂ misfit film was synthesized in this work through organic intercalation, exfoliation, and re-assembly techniques. The absolute value of Seebeck coefficient of the misfit film was significantly enhanced to 44.8 μV K^-1, which is five times higher than that of the original MXene film. This enhancement is attributed primarily to the weighted effect of the Seebeck coefficient and possibly to energy-filtering effects at the heterogeneous interfaces. Additionally, the power factor of the misfit film was considerably improved to 77.2 μW m^-1 K^-2, which is 18 times higher than that of the original MXene film. The maximum output power of the TE device constructed of the misfit film was 95 nW at a temperature difference of 40 K, resulting in a power density of 1.18 W m^-2, demonstrating the significant potential of this technology for driving low-energy consumption wearable electronics.