Low‐Symmetry PdSe₂ for High Performance Thermoelectric Applications

Abstract

As an emerging member in 2D materials, pentagonal palladium diselenide (PdSe 2) has interesting ambipolar charge transport behavior with high airstability and shows great potential in nanoelectronics and optoelectronics. Moreover, the puckered pentagon structure in PdSe 2 results in an intrinsic low lattice thermal conductivity, which makes PdSe 2 a superior material prospect for thermoelectric (TE) applications. However, its TE properties have yet to be experimentally demonstrated. Here, the TE transport in 2D PdSe 2 with a low-symmetry pentagonal lattice is probed for the first time. By thickness-engineering, it is demonstrated that the TE property of PdSe 2 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 PdSe 2 flakes. A power factor as high as 1.5 mW m −1 K −2 can be achieved for a PdSe 2 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 PdSe 2 opens up new pathways for TE applications, low-dimensional electronics, and quantum devices.

Gate‐Tunable Polar Optical Phonon to Piezoelectric Scattering in Few‐Layer Bi2O2Se for High‐Performance Thermoelectrics

“…This reinforces the fact that the PF behavior is actually dominated by carrier mobility, as opposed to carrier concentration modulation observed in most materials. [ 39,42 ] Nevertheless, for the temperature region below 100 K, the mobility changes much slowly with decreasing temperature and the drastic decrease in Seebeck coefficient (Figure S7, Supporting Information) starts to dominated the PF trend. [ 50,51 ] Remarkably, the peak values of PF we observed for different gate voltage are almost overlapped with the onset transition temperatures between piezoelectric scattering and polar optical phonon scattering and shows a sensitive dependence to gate voltage (i.e., shifts from under 80 K to 200 K for −10 and 70 V gate voltage, respectively) as shown in Figure 4b.…”

The Origin of Quantum Effects in Low‐Dimensional Thermoelectric Materials

“…To obtain the condition of , there are two strategies: 1) to design the size of the materials to decrease L ; 2) to reduce the effective mass of carrier to increase Λ. Here, we show the recent experimental works [ 15–17,62,63 ] that confirm the validity of for low‐dimensional materials by using the strategies.…”

“…The recent progress reports [9,[15][16][17], [62] also leaves us several take-home messages for future research directions to enhance the quantum confinement effects. The first message is to measure the value of Λ experimentally.…”

“…[76] It is noted that the condition of L∕Λ > 1 is based on a one-band model. [9] Furthermore, Zhao et al [62] showed for 2D PbSe 2 with 8 and 15 layers (L = 5 and 9 nm) that the observed PF are 1.3 and 1.1 mW m -1 K −2 at 200 K in which L∕Λ < 1 and > 1, Figure 5. Power factor, PF, of the 2D InSe as a function of the ratio between L and Λ with three different carrier concentrations.…”

“…[ 9 ] Furthermore, Zhao et al. [ 62 ] showed for 2D PbSe 2 with 8 and 15 layers ( and 9 nm) that the observed PF are 1.3 and 1.1 mW m ‐1 K −2 at 200 K in which and >1, respectively. Therefore, the condition can be an important experimental guideline for optimizing the thermoelectric devices based on the 2D layered materials.…”