Intrinsically High Thermoelectric Performance in AgInSe₂ n‐Type Diamond‐Like Compounds

Abstract

Diamond‐like compounds are a promising class of thermoelectric materials, very suitable for real applications. However, almost all high‐performance diamond‐like thermoelectric materials are p‐type semiconductors. The lack of high‐performance n‐type diamond‐like thermoelectric materials greatly restricts the fabrication of diamond‐like material‐based modules and their real applications. In this work, it is revealed that n‐type AgInSe2 diamond‐like compound has intrinsically high thermoelectric performance with a figure of merit (zT) of 1.1 at 900 K, comparable to the best p‐type diamond‐like thermoelectric materials reported before. Such high zT is mainly due to the ultralow lattice thermal conductivity, which is fundamentally limited by the low‐frequency Ag‐Se “cluster vibrations,” as confirmed by ab initio lattice dynamic calculations. Doping Cd at Ag sites significantly improves the thermoelectric performance in the low and medium temperature ranges. By using such high‐performance n‐type AgInSe2‐based compounds, the diamond‐like thermoelectric module has been fabricated for the first time. An output power of 0.06 W under a temperature difference of 520 K between the two ends of the module is obtained. This work opens a new window for the applications using the diamond‐like thermoelectric materials.

Thermoelectric properties of n-type Cu4Sn7S16-based compounds

“…In contrast, Ag doping slightly enhances n H . This is in line with the common phenomena that Ag-based chalcogenides tend to show n-type conduction, [30][31][32][33] which is probably related to the formation of more S vacancies or Ag interstitial atoms. The carrier mobility is 34 cm 2 V À1 s À1 for undoped sample and does not change much when doped ( Fig.…”

Slowing down the heat in thermoelectrics

“…Stacking faults have been extensively observed in metals with face‐centered‐cubic (FCC) and hexagonal close‐packed crystal structures, 22,204,205 and they are produced by crystal plane slip and vacancy collapsing or interstitial atom gathering on the close‐packed planes. In the thermoelectric field, stacking faults suppress phonon transport and reduce κ lat mainly by generating lattice distortions 206–209 . In tetragonal‐structured AgInSe 2 , typical stacking faults were detected, and dislocations, lattice distortions, and other crystal imperfections were noticed around these stacking faults (Figure 9(A,B)) 209 .…”

“…In the thermoelectric field, stacking faults suppress phonon transport and reduce κ lat mainly by generating lattice distortions 206–209 . In tetragonal‐structured AgInSe 2 , typical stacking faults were detected, and dislocations, lattice distortions, and other crystal imperfections were noticed around these stacking faults (Figure 9(A,B)) 209 . In the case of pure AgInSe 2 , they strongly scattered phonons and led to substantially lower κ lat when compared with the cases of the homologous compounds AgInTe 2 210 and CuInSe 2 211 ; moreover, they induced low‐phonon‐frequency Ag‐Se cluster vibrations in intrinsic AgInSe 2 209 (Figure 9(C)).…”

Silver vacancy concentration engineering leading to the ultralow lattice thermal conductivity and improved thermoelectric performance of Ag1-xInTe2

“…Therefore, it is quite necessary to explore novel TE candidates. Ternary I-III-VI 2 (I = Cu, Ag; III = Al, Ga, In; VI = S, Se, Te) chalcogenides, such as CuGaTe 2 1 , CuInTe 2 2 , AgInSe 2 3 and AgGaTe 2 4,5 , have recently attracted much attention in thermoelectrics because of their unique crystal and band structures 6,7 , among which the cation vacancy and crystal structure are two important factors in engineering both the carrier concentration and phonon transport 8–10 . However, to our best knowledge, AgInTe 2 has not received due recognition.…”