Surface Oxide Removal for Polycrystalline SnSe Reveals Near-Single-Crystal Thermoelectric Performance

Abstract

Nearly intrinsic charge and thermal transport properties of polycrystalline SnSe materials are unveiled for the first time. We confirm that tin oxide layers on the surface of SnSe powder are the origin of paradoxically higher apparent thermal conductivity in polycrystalline samples over single crystal. Our surface oxide removing strategy on polycrystalline SnSe materials reveals even lower thermal conductivity than single-crystal samples and simultaneously enhances the hole mobility, electrical conductivity, and Seebeck coefficient, leading to an extraordinarily high thermoelectric figure of merit (ZT) of 2.5.

Cu Intercalation and Br Doping to Thermoelectric SnSe2 Lead to Ultrahigh Electron Mobility and Temperature‐Independent Power Factor

“…[41] As a consequence, the means of improving TE performance for SnSe 2 or materials with similar crystal structure has been limited to suppressing lattice thermal conductivity via nanostructuring. [32,33] It even exceeds the value of the best performing n-type SnSe 0.985 Br 0.015 single crystals above ≈573 K. [47] Its engineering ZT (ZT eng ) is ≈0.25 for the temperatures of hot and cold sides at 300 and 773 K, respectively, which exceeds the any reported value for SnSe 2 -based materials. [44] However, it is hard to expect SnSe 2 to exhibit a lattice thermal conductivity as low as SnSe because Sn atoms in the SnSe 2 structure form a nearly ideal octahedron with Se ligands to give isotropic SnSe bond distances.…”

“…The theoretical Pisarenko relation between S and n H is plotted for pristine SnSe 2 at 300 (green line) and 773 K (red line) ( Figure S6, Supporting Information). 2020, 30,1908405 nanoplate-based pellet [43] and SnSe 2 -1.9 at% Cu nanocomposite [42] as well as the state-of-the-art bulk polycrystalline p-type Na 0.01 (Sn 0.95 Pb 0.05 ) 0.99 Se [33] and n-type SnSe 0.985 Br 0.015 single crystal [47] from the previous reports. [59] The S values at 300 and 773 K for SnCu x Se 2−y Br y (x = 0, 0.005 and y = 0, 0.02) in this work and SnSe 2−z Br z (z = 0.001-0.05) from the previous report [46] fit well on the lines, indicating that Cu and Br doping does not reduce the effective mass in the conduction band near the Fermi level.…”

“…[23][24][25][26][27] For extensive applications of TE technology, the prime interest of the TE community is being shifted toward the discovery of more economically viable and environmentally friendly materials. [33] These achievements clearly highlight the importance in the discovery of new materials. The Kanatzidis group reported in 2014 that ZT ≈ 2.6 at 913 K is obtained in undoped p-type single crystal samples of SnSe.…”

“…When abundant heat is supplied at low cost, TE modules with high PF materials could be more commercially viable at present because they can consistently produce a large output power density under the given temperature gradient. [28][29][30][31][32][33][34] The surprising example is tin monoselenide (SnSe), which had not been considered for TE applications because of seemingly high electrical resistivity. [16][17][18][19][20][21][22] Recently, PbSe-based TE materials have also been greatly improved with new innovative strategies.…”

Improved Thermoelectric Properties and Environmental Stability of Conducting PEDOT:PSS Films Post-treated With Imidazolium Ionic Liquids

“…The performance of TE materials largely depends on the dimensionless figure-of-merit (ZT), ZT = σ S 2 T/κ where σ is electrical conductivity, S is Seebeck coefficient, T is absolute temperature, and κ is thermal conductivity (Snyder and Toberer, 2011). More recently, traditional inorganic materials such as SnSe (Chang et al, 2018;Lee et al, 2019), PbTe (Tan et al, 2016;Chen et al, 2017), GeTe (Li et al, 2018), and Cu 2 Se 0.5 S 0.5 (Ren, 2017) with ZT values of over 2 have been reported. Despite their impressive TE performance, the drawbacks such as high cost, scarcity, toxicity, and low processability limit their commercial applications.…”