Interstitial Cu: An Effective Strategy for High Carrier Mobility and High Thermoelectric Performance in GeTe

Abstract

Dense point defects can strengthen phonon scattering to reduce the lattice thermal conductivity and induce outstanding thermoelectric performance in GeTe‐based materials. However, extra point defects inevitably enlarge carrier scattering and deteriorate carrier mobility. Herein, it is found that the interstitial Cu in GeTe can result in synergistic effects, which include: 1) strengthened phonon scattering, leading to ultralow lattice thermal conductivity of 0.48 W m−1 K−1 at 623 K; 2) weakened carrier scattering, contributing to high carrier mobility of 80 cm2 V−1 s−1 at 300 K; 3) optimized carrier concentration of 1.22 × 1020 cm−3. Correspondingly, a high figure‐of‐merit of ≈2.3 at 623 K can be obtained in the Ge0.93Ti0.01Bi0.06Te‐0.01Cu, which corresponds to a maximum energy conversion efficiency of ≈10% at a temperature difference of 423 K. This study systematically investigates the doping behavior of the interstitial Cu in GeTe‐based thermoelectric materials for the first time and demonstrates that the localized interstitial Cu is a new strategy to enhance the thermoelectric performance of GeTe‐based thermoelectric materials.

Recent advances, challenges, and perspective of copper‐based liquid‐like thermoelectric chalcogenides: A review

“…[150] By contrast, Cu interstitials has been found to facilitate carrier scattering and thus deteriorate carrier mobility, leading to maximized TE properties of GeTe. 47 Such phases further inhibit the formation of Cu vacancy in α-Cu 2 Se bulks and films, 149,221 for example, Figure 14A demonstrates that Cu/Se stoichiometric ratio has important role to reduce the Cu vacancies in Cu 2+x Se nanoplates. With largely filled Cu vacancies, the transformation of β-Cu 2 Se to α-Cu 2 Se comes from disordered Cu atoms in the ordered sublattice.…”

“…Due to Cu deficiency at elevated temperatures, mixture of phases in Cu 2 Se can co‐exist as reported in ref. [150] By contrast, Cu interstitials has been found to facilitate carrier scattering and thus deteriorate carrier mobility, leading to maximized TE properties of GeTe 47 . Such phases further inhibit the formation of Cu vacancy in α‐Cu 2 Se bulks and films, 149,221 for example, Figure 14A demonstrates that Cu/Se stoichiometric ratio has important role to reduce the Cu vacancies in Cu 2+ x Se nanoplates.…”

“…22,[37][38][39][40] In fact, investigation of many highperformance TE materials with substantially improved ZTs have been evident after Slack's concept of "phononglass electron-crystal" (PGEC) in 1990s. 41 Literatures reveal some potential PGEC systems such as MnTe, SnTe, poly-SnSe, In 0.25 Co 4 Sb 12 , Cu 2 Se-CuInSe 2 , GeTe, SiGe, Ca 3 Sb 2, and InSb etc., [42][43][44][45][46][47] however, the reported inferior electrical and thermal properties are still challenging due to their poor intrinsic properties. The periodic structures indicated the free transport of carriers, and a variety of cage-like compounds, that is, filled skutterudites and intermetallic clathrates have been studied as PGEC.…”

“…Literatures reveal some potential PGEC systems such as MnTe, SnTe, poly‐SnSe, In 0.25 Co 4 Sb 12 , Cu 2 Se‐CuInSe 2 , GeTe, SiGe, Ca 3 Sb 2, and InSb etc., 42–47 however, the reported inferior electrical and thermal properties are still challenging due to their poor intrinsic properties. The periodic structures indicated the free transport of carriers, and a variety of cage‐like compounds, that is, filled skutterudites and intermetallic clathrates have been studied as PGEC 48 .…”

Direct Current Treatment Tuning Crystallinity Leading to High-Performance p-Type Sb2Te3 Flexible Thin Films

“…Thermoelectric (TE) materials can realize direct energy conversion between electricity and heat and have demonstrated wide application potentials in the field of wearable electronics, chip sensors, and Internet of Things. − The TE power-generating performance of f-TFs can be evaluated by the power factor, S 2 σ, where S and σ are the Seebeck coefficient and electrical conductivity, respectively. , σ can be expressed as σ = n h e μ, where n h and μ represent the carrier concentration and carrier mobility, respectively, and e is the elementary charge. , Based on the Mott formula as shown in eq S1, S can be increased by reduced n h and enhanced effective mass ( m *). , However, the reduced n h also deteriorates the σ, which requires further optimization. − …”