Thermoelectric Properties of Strained β-Cu₂Se

Abstract

In recent years, the high-temperature phase of Cu 2 Se, namely, β-Cu 2 Se, has attracted increasing attention due to its outstanding thermoelectric efficiency. The Cu ions in β-Cu 2 Se show a distinct ion−liquid behavior between the framework of a Se ion lattice. Many experimental operations may lead to a discrepancy in the lattice structure. Experimentally synthesized β-Cu 2 Se was p-type, and a thermoelectric device needs both p-type and n-type materials with a close figure of merit. Studying the effect of strain and the possibility of n-type β-Cu 2 Se is essential. Utilizing first-principles calculations and molecular dynamics simulations, we investigate the thermoelectric performance of strained β-Cu 2 Se. The results show that the n-type β-Cu 2 Se can exhibit superior zT values like the p-type one. Applying compressive strain is an effective way to promote the power factor. The tensile strain will lead to a low lattice thermal conductivity and thus boost the p-type zT values. The predicted maximum zT values for n-type and p-type β-Cu 2 Se can reach 1.65 and 1.71 at 800 K, respectively. Considering the fact that applying strain is challenging in experiments, we propose a feasible strategy to manipulate the lattice structure and carrier type: doping halogen elements. Our results provide a guide for Cu 2 Se-based thermoelectric devices.

Strain-Induced Defect Evolution for the Construction of Porous Cu2–xSe with Enhanced Thermoelectric Performance

“…According to the phonon gas theory: k L = 1/3 C V vl , where C V , v , and l stand for the constant volume heat capacity, sound velocity, and phonon mean free path, respectively. The reduced lattice thermal conductivity could be attributed to the reduced sound velocity and enhanced phonon scattering, consistent with a previous report. , On the other hand, the ultralow lattice thermal conductivity should also be a consequence of dynamic defect evolution including Cu ionic diffusion to dissipate energy. ,− As shown in Figure d, because the reduced electrical properties were compensated for by the diminished thermal conductivity, all porous Cu 2– x Se had a higher ZT than that of the dense samples. As a result, a maximum ZT of 1.30 was achieved in the porous Cu 1.92 Se sample at 800 K, which was an improvement of 42%.…”

Strengthened phonon scattering and band convergence synergistically realize the high-performance SnTe thermoelectric

“…(Cu, Ag) 2 X (X = S, Se, or Te) compounds with extremely low k lat are regarded as the "phonon-liquid, electron-crystal" (PLEC) materials and have been adopted to suppress the k lat of TE materials. [41][42][43][44][45] For example, Cu 2 Te alloying in SnTe and Cu 2 Se alloying in Bi 2 Te 3 can introduce both Cu substitutional and interstitial defects, and thus signicantly reduce the k lat . [46][47][48][49][50][51][52] AgCuTe is another "PLEC" material and it is generally considered that Ag and Cu may randomly arrange in the cation sites and produce various point defects to decrease the k lat of TE materials, such as Bi 0.48 Sb 1.52 Te 3 .…”

Efficient photo-assisted Fenton-like reaction of yolk–shell CuSe(Cu2Se)/g-C3N4 heterojunctions for methylene blue degradation

“…Copper selenide is a wideband p-type semiconductor 11 with unique thermoelectric, 21 Seebeck, 22 and photo-electric 23 effects and is widely applied to solar cells 24 because of adjustable stoichiometric ratios (CuSe, Cu 2 Se, Cu 3 Se 2 , and Cu 2−x Se) [12][13][14][15] and different types of crystallographic systems: cubic, tetragonal, single monocline, and hexagonal structures. [16][17][18][19][20] In addition, copper selenide quantum dots have been used in traditional photocatalysis because of their high specic surface area, crystallinity, and small particle size.…”