(GeTe)_1–x(AgSnSe₂)_x: Strong Atomic Disorder-Induced High Thermoelectric Performance near the Ioffe–Regel Limit

Abstract

In thermoelectrics, the material’s performance stems from a delicate tradeoff between atomic order and disorder. Generally, dopants and thus atomic disorder are indispensable for optimizing the carrier concentration and scatter short-wavelength heat-carrying phonons. However, the strong disorder has been perceived as detrimental to the semiconductor’s electrical conductivity owing to the deteriorated carrier mobility. Here, we report the sustainable role of strong atomic disorder in suppressing the detrimental phase transition and enhancing the thermoelectric performance in GeTe. We found that AgSnSe2 and Sb co-alloying eliminates the unfavorable phase transition due to the high configurational entropy and achieve the cubic Ge1–x–y Sb y Te1–x (AgSnSe2) x solid solutions with cationic and anionic site disorder. Though AgSnSe2 substitution drives the carrier mean free path toward the Ioffe–Regel limit and minimizes the carrier mobility, the increased carrier concentration could render a decent electrical conductivity, affording enough phase room for further performance optimization. Given the lowermost carrier mean free path, further Sb alloying on Ge sites was implemented to progressively optimize the carrier concentration and enhance the density-of-state effective mass, thereby substantially enhancing the Seebeck coefficient. In addition, the high density of nanoscale strain clusters induced by strong atomic disorders significantly restrains the lattice thermal conductivity. As a result, a state-of-the-art zT ≈ 1.54 at 773 K was attained in cubic Ge0.58Sb0.22Te0.8(AgSnSe2)0.2. These results demonstrate that the strong atomic disorder at the high entropy scale is a previously underheeded but promising approach in thermoelectric material research, especially for the numerous low carrier mobility materials.

Realizing High Energy Conversion Efficiency in a Novel Segmented‐Mg3(Sb, Bi)2/Cubic‐GeTe Thermoelectric Module for Power Generation

“…f) Comparison of average zT values between Ge 0.83 Mn 0.09 Ti 0.02 Bi 0.06 Te and some other reported cubic-GeTe-based materials with different compositions. [35,36,[39][40][41][42][43] composition Mg 3.1 Co 0.1 Sb 1.5 Bi 0.49 Te 0.01 and cubic GeTe was also prepared for comparison with the segmented unicouple. Load voltage, output power, heat flow out of the cold side, and conversion efficiency of the prepared module were measured as functions of electrical current at different hot-side temperatures and the results are shown in Figure 3a-d.…”

“…Temperature-dependent a) electrical conductivity, b) Seebeck coefficient, c) power factor (PF = S 2 σ), d) thermal conductivity, and e) zT of the prepared GeTe samples with different compositions. f) Comparison of average zT values between Ge 0.83 Mn 0.09 Ti 0.02 Bi 0.06 Te and some other reported cubic-GeTe-based materials with different compositions [35,36,[39][40][41][42][43].…”

Research on the Influence of the Interfacial Properties Between a Cu3BiS3 Film and an InxCd1−xS Buffer Layer for Photoelectrochemical Water Splitting

“…Figure S8d and Table 1 shows that In 0.6 Cd 0.4 S has the lowest slope, which indicates that its carrier concentration is relatively high and suggests that the buffer layer of In 0.6 Cd 0.4 S has excellent electrical performance and will improve the ability of electrons to be extracted from the Cu 3 BiS 3 absorption layer and then facilitate the proton reduction reaction. [25]…”

Boosting Thermoelectric Performance in Epitaxial GeTe Film/Si by Domain Engineering and Point Defect Control

“…The lower p value of the L-sample is likely attributed to the reduction of the V Ge , which comes from the film growth under the situation that Te is easily volatilized. As shown in Figure a, the L-sample exhibited relatively high μ comparable to polycrystalline GeTe bulks ,,,− at almost the same p , and higher μ than that of the polycrystalline GeTe thin films . Therefore, the L-sample exhibited almost the same σ tendency against p as polycrystalline GeTe bulks unlike polycrystalline GeTe films (Figure b).…”

“…We also measured the electrical properties of the L-sample. Figure a–c shows μ, σ, and S as a function of p at 300 K, respectively, where the data from the preceding studies were also plotted simultaneously. ,,,− The average p value of the L-sample was ∼3 × 10 20 cm –3 , which was lower than those of polycrystalline GeTe bulks (∼4–9 × 10 20 cm –3 ) ,,− and polycrystalline GeTe thin films (∼1–3 × 10 21 cm –3 ) . Furthermore, this p value was lower than or comparable to those of polycrystalline GeTe bulks containing an extra number of Ge (∼3–5 × 10 20 cm –3 ) .…”