Cation disorder and bond anharmonicity synergistically boosts the thermoelectric performance of p-type AgSbSe₂

Abstract

AgSbSe2 is one of the important Te-free chalcogenides in I-V-VI2 semiconductors, shows attractive functional properties with enhancing thermoelectric performance. Here we report the thermoelectric performance of polycrystalline p-type AgSbSe2¬ nanostructured...

Advances and Challenges of AgSbSe2‐based Thermoelectric Materials

“…clarified that the above mentioned “minimum thermal conductivity” in I‐V‐VI 2 semiconductors is limited solely by phonon‐phonon interactions [57] . Many studies have been performed to rationalize such a high thermal resistance, [53,57–60] and, as schematically shown in Figure 3, the underlying physical origins can be assigned to the following three reasons:…”

“…In AgSbSe 2 , the valence electron configuration of Sb is 5 s 2 5p 3 , wherein only 5p 3 electrons are sharing to form a polar covalent bond with Se valence electrons while the 5s 2 electrons of Sb becomes a lone pair. [53,60,62] Numerous studies [41,56,58,59,63,64] have unambiguously demonstrated that the strong hybridization and repulsion between the lone-pair 5s 2 electrons of the group V cation and the valence p orbitals of the group VI anion lead to soft phonon modes and therefore reduced thermal conductivity. 3) Strong phonon-phonon interactions resulting from the high degree of anharmonicity in SbÀ Se bonding arrangement.…”

“…Recently, it is revealed that synthesis condition also plays a role in tuning the carrier concentration of AgSbSe 2 . [41,60,73,75] Gao et al [73] found that the ball-milled nanostructuring AgSbSe 2 has higher carrier concentration (1.6 × 10 19 cm À 3 ) than its coarsegrained ingots (0.6 × 10 19 cm À 3 ) at room temperature. As a strong plastic deformation process, ball-milling usually induces rich defects in samples and induces changes of carrier density.…”

“…Since Ag and Sb atoms are located in identical crystallographic positions with various valence electrons configurations, [61] nanosized violations of crystalline lattice periodicity emerge in the regions enriched with Ag or Sb resulting in increased phonon scattering centers. Large lattice anharmonicity originating from stereochemically active lone pairs of Sb. In AgSbSe 2 , the valence electron configuration of Sb is 5 s 2 5p 3 , wherein only 5p 3 electrons are sharing to form a polar covalent bond with Se valence electrons while the 5s 2 electrons of Sb becomes a lone pair [53,60,62] . Numerous studies [41,56,58,59,63,64] have unambiguously demonstrated that the strong hybridization and repulsion between the lone‐pair 5s 2 electrons of the group V cation and the valence p orbitals of the group VI anion lead to soft phonon modes and therefore reduced thermal conductivity. Strong phonon‐phonon interactions resulting from the high degree of anharmonicity in Sb−Se bonding arrangement.…”

“…Recently, it is revealed that synthesis condition also plays a role in tuning the carrier concentration of AgSbSe 2 [41,60,73,75] . Gao et al [73] .…”