Journal
ADVANCED SCIENCE
Volume 9, Issue 20, Pages -Publisher
WILEY
DOI: 10.1002/advs.202103720
Keywords
electrical resistivity; high pressure; SnSe; transmission electron microscopy; thermoelectric power
Categories
Funding
- Ministry of Science and Higher Education of the Russian Federation [122021000039-4]
- RFBR [20-02-00695]
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Manipulating stress can greatly enhance the thermoelectric power factor and narrow the band gap of layered SnSe single crystals, offering a novel approach to improve the performance of thermoelectric materials.
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 approximate to 180 mu W 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.
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