Engineering of charge carriersviaa two-dimensional heterostructure to enhance the thermoelectric figure of merit

Abstract

High band degeneracy and glassy phonon transport are two remarkable features of highly efficient thermoelectric (TE) materials. The former promotes the power factor, while the latter aims to break the lower limit of lattice thermal conductivity through phonon scattering. Herein, we use the unique possibility offered by a two-dimensional superlattice-monolayer structure (SLM) to engineer the band degeneracy, charge density and phonon spectrum to maximize the thermoelectric figure of merit (ZT). First-principles calculations with Boltzmann transport equations reveal that the conduction bands of ZrSe2/HfSe2 SLM possess a highly degenerate level which gives a high n-type power factor; at the same time, the stair-like density of states yields a high Seebeck coefficient. These characteristics are absent in the individual monolayers. In addition, the SLM shows a suppressed lattice thermal conductivity along the superlattice period as phonons are effectively scattered by the interfaces. An intrinsic ZT of 5.3 (300 K) is achieved in n-type SLM, and it is 3.2 in the p-type counterpart. Compared with the theoretical predictions calculated with the same level of accuracy, these values are at least four-fold higher than those in the two parent materials, monolayer ZrSe2 and HfSe2. Our results provide a new strategy for the maximum thermoelectric performance, and clearly demonstrate the advantage of two-dimensional material heterostructures in the application of renewable energy.

Significant enhancement of the thermoelectric properties of CaP3 through reducing the dimensionality

“…7, the calculated ZT as a function of chemical potential for CaP 3 is presented at typical temperatures of 300, 500 and 700 K. Surprisingly, we find that the maximum value of ZT at 700 K can reach 6.39 along a direction for monolayer, which is markedly higher than that of the bulk phase ∼2.83. Such high ZT value can comparable to several star TE materials, such as ZrSe 2 /HfSe 2 superlattice-monolayer structure (ZT = 5.3 at 300 K) 73 , thin-film Fe 2 V 0.8 W 0.2 Al (ZT = 5 around 300-400 K) 74 , monolayer SnP 3 (6.10 at 500 K) 75 and InP 3 (5.16 at 700 K) 33 .…”

Few-Layer PdSe2 Sheets: Promising Thermoelectric Materials Driven by High Valley Convergence

“…Here, we adopted this value and used m * as 0.19 m e in our calculation. 49 The carrier concentration ( n ) is defined asHere, rigid-band approximation 68 is used, which assumes that the shape of the band structure does not change under light doping, but only shifts the Fermi level up (down) for n-type (p-type) doping, respectively.…”

Type‐II AsP/As van der Waals Heterostructures: Tunable Anisotropic Electronic Structures and Optical Properties

“…Therefore, by integrating together the virtue of its building monolayers, the vdW heterostructures have the opportunity to provide a versatile platform for exploring new phenomena and designing novel materials for high‐performance electronic devices, [ 4–8 ] optoelectronic device, [ 9 ] chemical sensors, [ 10 ] water‐splitting photocatalysts, [ 11–13 ] and thermoelectric generators. [ 14 ]…”