Progressive Regulation of Electrical and Thermal Transport Properties to High‐Performance CuInTe₂ Thermoelectric Materials

Abstract

In addition, it is of importance to note that a high power factor ( S 2 / ρ ) is also indispensable for a given TE material to maximize its output power. [ 3 ] Therefore, by taking account of the practical application, a simultaneously optimization in the electrical and thermal transport properties of TE materials is imperative to maximize the output power and conversion efficiency concurrently. Recently, some strategies have been proved to be effective and even high ZT values greater than 2.0 have been achieved in the Pb-based TE materials, [ 4,5 ] such as the band convergence, [ 6 ] electronic density of states (DOS) distortion, [ 7 ] carrier energy barrier fi ltering, [ 8 ] and the conduction (valence) band modifi cation [ 9 ] to enhance Seebeck coefficient for high power factor; while defect engineering, [ 10 ] nanostructuring, [ 11 ] and multiscale hierarchical architecturing [ 12 ] to enhance the scattering of phonons for low thermal conductivity. However, the environmentally hazardous Pb element prevents them from widespread application. Therefore, it is of signifi cance to develop eco-friendly TE materials for middle temperature application, such as Mg 2 Si, [ 13 ] Half-Heusler, [ 14 ] and BiCuSeO [ 15 ] based TE materials.More recently, chalcopyrite CuInTe 2 is being considered as a promising p-type TE material because of the merits of environmentally friendly chemical component, intrinsically high electrical conductivity, and high Seebeck coeffi cient owing to the degenerate energy bands near the valence band maximum (VBM). [ 16 ] Thus many efforts have been made theoretically and experimentally [17][18][19][20][21][22] to enhance its TE performance already, such as Cu defi ciency and cation substitution. However, since there are two cation sites (Cu and In) in CuInTe 2 , cation substitution often lacks specifi city and may generate both electron and hole simultaneously, making it diffi cult to enhance the electrical transport properties substantially. Besides, the less phonon scattering, mainly by point defects originated from chemical component regulation, rendering its thermal conductivity is still relatively high. It is well known that refi ning the microstructure into nanoscale is often effective in optimizing thermal transport properties, yet the electrical transport properties are usually deteriorated due to the inevitably scattering of carriers, as typical shown in the CuInTe 2 /graphene [ 23 ] and our

Fine Art of Thermoelectricity

“…6 So far, the thermoelectric community is focused on bulk inorganic semiconductors, such as metal chalcogenides, for example, Bi 2 Te 3 -based materials, which are used in the most efficient and stable thermoelectric devices. 7,8 These conventional thermoelectric materials are expensive, energy-consuming in preparation, and environmentally hazardous. On the other hand, conductive conjugated polymers 9 and organic− inorganic hybrid nanocomposites, such as polymer/carbon nanotubes, 10 turn out to be very promising materials that can be implemented in large-scale, low-cost, and flexible thermoelectric elements based on thin-film architectures.…”

Copper chalcogenide thermoelectric materials

“…3a, Cu 2 Se possesses two sublattices: the rigid FCC framework of Se atoms and the disordered and flowing sublattice of Cu. At high temperatures, Cu ions migrate from one site (interstitial one formed by Se) to another, exhibiting a flowing character that is Figure 1 Timeline of zT for selected Cu-based superionic conductors [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] (red), tetragonal [28][29][30][31][32][33][34][35][36][37] (blue) and distorted [38][39][40][41][42][43][44][45][46][47][48][49] (green) diamond-like materials and BiCuSeO oxyselenides (purple) [50][51][52][53][54][55][56][57][58][59]…”

“…In addition, the nanostructuring approach was also employed [133,134]. The enhanced thermoelectric performance can be attributed to the phonon scattering introduced by crystal defects and the increased density of states near the Fermi level, such as (CuInTe 2 ) 0.99 (ZnTe) 0.01 composited with 0.1 wt% TiO 2 nanofiber (zT~1.47 at 823 K) [135], CuInTe 2 composited ZnO (zT~1.61 at 823 K) [34].…”

Synergistic Regulation of Phonon and Electronic Properties to Improve the Thermoelectric Performance of Chalcogenide CuIn1−xGaxTe2:yInTe (x = 0–0.3) with In Situ Formed Nanoscale Phase InTe

“…Unfortunately, the power factors do not increase significantly. [31,32] Recently, we have developed several kinds of Cu-In-Te derivatives, such as (Cu 2 Te) δ Cu 1. [31,32] Recently, we have developed several kinds of Cu-In-Te derivatives, such as (Cu 2 Te) δ Cu 1.…”

“…After implementing this strategy, the power factor increases to 13.8 µW m −1 K −2 at ≈687 K, about 73% enhancement compared to the pristine CuInTe 2 , [31] and at the same time the lattice part κ L reduces to 0.61 W m −1 K −1 at ≈854 K, decreasing by a factor of 2. After implementing this strategy, the power factor increases to 13.8 µW m −1 K −2 at ≈687 K, about 73% enhancement compared to the pristine CuInTe 2 , [31] and at the same time the lattice part κ L reduces to 0.61 W m −1 K −1 at ≈854 K, decreasing by a factor of 2.…”