Giant Room‐Temperature Power Factor inp‐Type Thermoelectric SnSe under High Pressure

Abstract

Materials that can efficiently convert heat into electricity are widely utilized in energy conversion technologies. The existing thermoelectrics demonstrate rather limited performance characteristics at room temperature, and hence, alternative materials and approaches are very much in demand. Here, it is experimentally shown that manipulating an applied stress can greatly improve a thermoelectric power factor of layered p-type SnSe single crystals up to ≈180 μW K −2 cm −1 at room temperature. This giant enhancement is explained by a synergetic effect of three factors, such as: band-gap narrowing, Lifshitz transition, and strong sample deformation. Under applied pressure above 1 GPa, the SnSe crystals become more ductile, which can be related to changes in the prevailing chemical bonding type inside the layers, from covalent toward metavalent. Thus, the SnSe single crystals transform into a highly unconventional crystalline state in which their layered crystal stacking is largely preserved, while the layers themselves are strongly deformed. This results in a dramatic narrowing in a band gap, from E g = 0.83 to 0.50 eV (at ambient conditions). Thus, the work demonstrates a novel strategy of improving the performance parameters of chalcogenide thermoelectrics via tuning their chemical bonding type, stimulating a sample deformation and a band-structure reconstruction.

Controlling the semiconductor–metal transition in Cu-intercalated TiSe2 by applying stress

“…More details can be found in previous papers. 61,62 ambient conditions; 6,[19][20][21]26 meanwhile, negative Seebeck coefficients of about À(3-9) mV K À1 were also reported in the literature. 17,25,27 Two TiSe 2 crystals we studied (labelled as #1 and #2) had slightly different Seebeck coefficients under ambient conditions (Fig.…”

“…Standardized toroidal-shaped containers made of limestone served both as gaskets and as pressure-transmitting media. 58,60,61 Samples of typical sizes of B150 Â 150 Â 150 mm 3 were loaded in a hole drilled in the centre of a limestone container (Fig. 4a and b).…”

“…4a and b). 58,61,62 We cut the samples from interiors of the as-grown single-crystalline ingots (Fig. 3) and selected those with suitable sizes.…”

When IV−VI Meets I−V−VI2: A Reinvigorating Thermoelectric Strategy for Tin Monochalcogenides

“…At temperatures above 800 K or pressures above 10 GPa, β‐SnSe, which also has an orthorhombic structure ( Cmcm , No. 63), becomes stable and shows higher symmetry with a less distorted lattice, in which each atom is bonded to five neighboring atoms of the opposite type [42,44] . The band structure of α‐SnSe is presented in Figure 2(b) [45] .…”

“…63), becomes stable and shows higher symmetry with a less distorted lattice, in which each atom is bonded to five neighboring atoms of the opposite type. [42,44] The band structure of α-SnSe is presented in Figure 2(b). [45] Unlike SnTe, α-SnSe intrinsically has an indirect band gap; the band gap is calculated to be ~0.61 eV.…”