A Self‐Independent Binary‐Sublattice Construction in Cu₂Se Thermoelectric Materials

Abstract

The atomic‐scale structure of cuprous selenide room temperature phase (α‐Cu2Se), which plays an important role in understanding the mechanism of its high thermoelectric performance, is still not fully determined. Here, direct observation with atomic‐scale resolution is realized to reveal the fine structure of α‐Cu2Se via spherical‐aberration‐corrected scanning transmission electron microscopy. It is observed to be an interesting self‐independent binary‐sublattice construction for Cu and Se in α‐Cu2Se, respectively, which shows a variety of ordered copper fluctuation structures are embedded in a rigid pseudo‐cubic Se sublattice. Ordering of Cu uses a variety of configurations with little energy difference, forming considerable amounts of “boundaries,” which may lead to ultrastrong phonon scattering. Furthermore, density functional theory calculations indicate that the electronic structures are mainly determined by the rigid Se face‐centered cubic sublattice and not sensitive to the various copper fluctuations, which may guarantee the electron transfers with large carrier mobility. The self‐independent binary‐sublattice construction is speculated to enhance phonon scattering while still maintaining good electrical transport property. This study provides new critical information for further understanding the possible correlation between the specific structure and thermoelectric performance of α‐Cu2Se, as well as designing new thermoelectric materials.

Advances in Nanoparticle-Enhanced Thermoelectric Materials from Synthesis to Energy Harvesting: A Review

“…This configuration maintains optimal electron transport efficiency while enhancing phonon scattering. These findings provide insight into methods for improving the thermoelectric performance of materials in future designs . In 2023, Zhi et al discovered that by doping Cu2Se with S and Te the material’s electronic band structure becomes more aligned, resulting in improved carrier mobility and power factor.…”

“…These findings provide insight into methods for improving the thermoelectric performance of materials in future designs. 45 In 2023, Zhi et al discovered that by doping Cu2Se with S and Te the material’s electronic band structure becomes more aligned, resulting in improved carrier mobility and power factor. Additionally, the presence of scattered second-phase features, dislocations, and nanograins further enhances its performance.…”

Ion transport induced room-temperature insulator–metal transition in single-crystalline Cu2Se

“…Previous experiments and theoretical work indicate that pristine Cu 2 Se is a semiconductor 36 with a ∼1.2 eV energy gap. 37 By removing a fraction of Cu ions from the unit cell, the Fermi level can be lowered with respect to the valence band maximum. 38,39 Despite the band shape not being altered significantly, lowering the Fermi level leads to significant manipulation of the electrical conductivity.…”