Simultaneous Enhancement of the Power Factor and Phonon Blocking in Nb-Doped WSe₂

Abstract

Transition-metal dichalcogenide WSe 2 is a potentially good thermoelectric (TE) material due to its high thermopower (S). However, the low electrical conductivity (σ), power factor (PF), and relatively large lattice thermal conductivity (κ L ) of pristine WSe 2 degenerate its TE performance. Here, we show that through proper substitution of Nb for W in WSe 2 , its PF can be increased by ∼10 times, reaching 5.44 μW cm −1 K −2 (at 850 K); simultaneously, κ L lowers from 1.70 to 0.80 W m −1 K −1 . Experiments reveal that the increase of PF originates from both increased hole concentration due to the replacement of W 4+ by Nb 3+ and elevated thermopower (S) caused by the enhanced density of states effective mass, while the reduced κ L comes mainly from phonon scattering at point defects Nb W . As a result, a record high figure of merit ZT max ∼0.42 is achieved at 850 K for the doped sample W 0.95 Nb 0.05 Se 2 , which is ∼13 times larger than that of pristine WSe 2 , demonstrating that Nb doping at the W site is an effective approach to improve the TE performance of WSe 2 .

Low Thermal Conductivity and High Thermoelectric Performance of Nb-Doped Quarternary Mixed Crystal Nb0.05W0.95-xMox(Se1–xSx)2

“…(a) Temperature-dependent electrical conductivity for all samples of Nb 0.05 W 0.95– y Mo y (Se 1– y S y ) 2 solid solution along with pristine WSe 2 , (b) variation of carrier mobility (μ) and carrier concentrations ( p ) at 300 K along MoS 2 content y , (c) temperature-dependent S for all MC samples and the inset represents the thermopower ( S ) for pure WSe 2 (inset in Figure c, reproduced with permission, Copyright 2023, American Chemical Society), and (d) variation of S with hole carrier concentration ( p ) (Pisarenko relationship) at room temperature; therein, the computed effective mass ( m d * ) is also given.…”

“…All of the S coefficients are positive, which indicates p-type semiconducting behavior. Furthermore, S behaves similarly at all temperatures for all specimens, the absolute coefficient of S in all samples rises with a rise in temperature as its highest temperature T = 850 K, indicating that these MC samples belong to degenerate semiconductors, in contrast with pure WSe 2 , whose S reduces with enhancing temperature (the inset in Figure c). The difference in the S behavior between pristine WSe 2 and MC samples arises from their distinct electronic structures.…”

“…The reduction in the lattice thermal conductivity is determined to be caused by the phonons scattering at the doping element. As a result, the dopant specimen achieves a high ZT ∼ 0.42 at 850 K . However, all previous researches on WSe 2 bulk samples were mainly focused on the improvement of its PF, and few of them were successful in the large reduction of its lattice thermal conductivity κ L .…”

Effect of niobium doping on excitonic dynamics in MoSe2

“…The charge transport properties of niobium-doped TMDs in field-effect transistors have also been explored [43,44,48,[60][61][62][63]. Furthermore, niobium doping has enhanced the performance of TMD-based devices in photodetection [64], photovoltaic [40,65,66], thermoelectric [67], and electrocatalytic hydrogen evolution devices based on TMDs [45].…”

M2+-Doped Nickel Selenide Nanoflowers (M = Co, Cu, and Zn) for Supercapacitors

“…Transition-metal doping engineering is a kind of important path to regulate the structure of nonmetallic material. To be specific, dopants can introduce plenty of structural defects, change the lattice parameters, supply abundant active sites, enhance the intrinsic electrical conductivity, improve the charge transportation between the host and heteroatom, as well as optimize the surface and interface electronic structure. − Therefore, doping engineering has been extensively used to enhance the supercapacitor properties of TMSes. − So far, several TMSes with various nanostructures and compositions have been successfully doped with metal dopants via several effective methods, such as hot injection, hydrothermal/solvothermal method, electrochemical deposition, chemical vapor deposition, chemical bath deposition, pulsed laser deposition, and so on. − However, there are still some issues to be solved, involving special equipment, high reaction temperature, long reaction time, utilization of organic solvents, complex purification process, obscure reaction mechanism, heterogeneous distribution of dopants, and so on . More importantly, the existing reports mainly focus on the study of doping with a metal dopant.…”