Graphene-Mediated Contact Engineering for a High Thermoelectric Performance in 2D PdSe ₂

Although theoretical studies have predicted that two-dimensional (2D) thermoelectric (TE) materials can significantly outperform their bulk counterparts, experimental measurements often fall short of expectations. The inherently high surface-to-volume ratio of 2D materials introduces substantial contact resistance, which severely obscures the evaluation of their intrinsic TE properties. Herein, we propose an architecture that incorporates few-layer graphene as electrodes, with a few-layer palladium diselenide (PdSe₂) channel and full hexagonal boron nitride (h-BN) encapsulation. This contact-engineered field-effect transistor exhibits significantly reduced contact resistance and enhanced electrical performance. Meanwhile, this contact engineering overcomes the trade-off between conductivity and Seebeck coefficient in few-layer PdSe₂, leading to synergistic enhancement. Ultimately, we achieve PF ≈ 1.55 mW m^-1 K^-2 at room temperature in 2D PdSe₂ system, representing one of the highest values among all reported. This work offers an approach for accurately probing the intrinsic TE properties of 2D TE materials and underscores the importance of contact engineering in future high-efficiency TE devices.