Low‐Symmetry PdSe2 for High Performance Thermoelectric Applications

Abstract As an emerging member in 2D materials, pentagonal palladium diselenide (PdSe2) has interesting ambipolar charge transport behavior with high air‐stability and shows great potential in nanoelectronics and optoelectronics. Moreover, the puckered pentagon structure in PdSe2 results in an intrinsic low lattice thermal conductivity, which makes PdSe2 a superior material prospect for thermoelectric (TE) applications. However, its TE properties have yet to be experimentally demonstrated. Here, the TE transport in 2D PdSe2 with a low‐symmetry pentagonal lattice is probed for the first time. By thickness‐engineering, it is demonstrated that the TE property of PdSe2 can be effectively manipulated due to its sensitive dependence on the interlayer coupling originating from the special lattice structure. The TE performance can be largely enhanced benefiting from the high band convergence and quantum confinement in thinner PdSe2 flakes. A power factor as high as 1.5 mW m−1 K−2 can be achieved for a PdSe2 flake with a thickness of 5 nm. This work provides the first TE study on a pentagonal lattice as opposed to hexagonal lattices that dominate the 2D layered material family. The unique lattice structure with special interlayer interaction in PdSe2 opens up new pathways for TE applications, low‐dimensional electronics, and quantum devices.