High Thermoelectric Performance of New Rhombohedral Phase of GeSe stabilized through Alloying with AgSbSe₂

Abstract

GeSe is a IV-VI semiconductor, like the excellent thermoelectric materials PbTe and SnSe. Orthorhombic GeSe has been predicted theoretically to have good thermoelectric performance but is difficult to dope experimentally. Like PbTe, rhombohedral GeTe has a multivalley band structure, which is ideal for thermoelectrics and also promotes the formation of Ge vacancies to provide enough carriers for electrical transport. Herein, we investigate the thermoelectric properties of GeSe alloyed with AgSbSe , which stabilizes a new rhombohedral structure with higher symmetry that leads to a multivalley Fermi surface and a dramatic increase in carrier concentration. The zT of GeAg Sb Se reaches 0.86 at 710 K, which is 18 times higher than that of pristine GeSe and over four times higher than doped orthorhombic GeSe. Our results open a new avenue towards developing novel thermoelectric materials through crystal phase engineering using a strategy of entropy stabilization of high-symmetry alloys.

Unraveling a novel ferroelectric GeSe phase and its transformation into a topological crystalline insulator under high pressure

“…It is also noted that laser heating is critical for synthesizing the R3m phase of GeSe; the phase transition only occurs through melting and crystallization under pressure. Furthermore, a rhombohedral phase similar to our R3m phase was recently observed in GeSe-AgSbSe 2 alloys 32 . As alloying GeSe with AgSbSe 2 may be regarded as an internal chemical pre-compression, the observation of this rhombohedral phase represents additional indirect evidence for our work.…”

1D/3D Alloying Induced Phase Transition in Light Absorbers for Highly Efficient Sb2Se3 Solar Cells

“…This also suggests that when Ag atoms diffuse into the ribbon‐like Sb 2 Se 3 system, the Ag atoms preferentially occupy the Sb sites and create substitutional disorder, and this increasing disorder leads to the enhancement of configurational entropy and the formation of the highly symmetric cubic ternary AgSbSe 2 phase. This behavior due to which (Sb 2 Se 3 ) x (AgSbSe 2 ) 1− x alloy is formed rather than Ag‐doped Sb 2 Se 3 is similar to the phenomenon generally found in high‐entropy thermoelectric alloys, where the stabilization of high‐symmetry phases is enhanced by adding extra elements to increase the entropy of the alloy system . Raman spectroscopy confirms this structural phase transition.…”

Review of high entropy ceramics: design, synthesis, structure and properties

“…Recent studies also show that entropy favors a rhombohedral-to-cubic structure transition in GeSe, when AgSbSe 2 (ref. 93) or AgBiSe 2 (ref. 94) was added to increase the entropy of the system.…”