Enhanced figure of merit of polycrystalline PtSe₂/PtSe₂ structures at room temperature by a facile wet-transfer stacking method

We report a promising strategy to enhance the in-plane thermoelectric (TE) figure of merit (ZT) of few-layer semimetallic PtSe₂ films at 300 K by piling up PtSe₂ layers with the same thickness (3 nm) as stacked PtSe₂/PtSe₂ (3-nm/3-nm) homostructures by a wet-transfer method. We observed that the Seebeck coefficient was enhanced meaningfully upon increasing the number of stacked layers and exceeded ~ 173.2 μV/K with a relatively constant electrical conductivity of ~ 18.4 S/cm at 300 K. By contrast, as the number of layers increased, thermal conductivity also showed a significant reduction, and ultimately, the ZT factor increased by ~ 380% compared to the single-stacked PtSe₂ structure. Such an increase in the ZT factor shows the possibility of a considerable improvement in the TE properties of semimetallic PtSe₂ with a new technique called facile wet-transfer stacking. The proposed method is expected to play a very important role in future microscopic cooling and energy-generating TE device applications.