Design and Fabrication of Segmented GeTe/(Bi,Sb)₂Te₃ Thermoelectric Module with Enhanced Conversion Efficiency

Abstract

GeTe and (Bi,Sb) 2 Te 3 are two representative thermoelectric (TE) materials showing maximum performance at middle and low temperature, respectively. In order to achieve higher performance over the whole temperature range, their segmented one-leg TE modules are designed and fabricated by one-step spark plasma sintering (SPS). To search for contact and connect layers, the diffusion behavior of Fe, Ni, Cu, and Ti metal layers in GeTe is studied systematically. The results show that Ti with a similar linear expansivity (10.80 × 10 −6 K −1 ) to GeTe, has low contact resistance (3 µΩ cm 2 ) and thin diffusion layer (0.4 µm), and thus is an effective metallization layer for GeTe. The geometric structure of the GeTe/(Bi,Sb) 2 Te 3 segmented one-leg TE module and the ratio of GeTe to (Bi,Sb) 2 Te 3 are determined by finite element simulation method. When the GeTe height ratio is 0.66, its theoretical maximum conversion efficiency (η max ) can reach 15.9% without considering the thermal radiation and thermal/electrical contact resistance. The fabricated GeTe/(Bi,Sb) 2 Te 3 segmented one-leg TE module showed a η max up to 9.5% with a power density ≈ 7.45 mW mm −2 , which are relatively high but lower than theoretical predictions, indicating that developing segmented TE modules is an effective approach to enhance TE conversion efficiency.

Exceptional figure of merit achieved in boron-dispersed GeTe-based thermoelectric composites

“…2d . Figure 1a shows the interfacial band diagram of the boron and GeTe, showing the work functions of two materials (GeTe: ~5.09 eV 43 , boron: ~4.45 eV 44 ). The interface contact between the matrix and the boron inclusion is exactly a p-p homojunction.…”

“…31 ). The output power density and conversion efficiency of the segmented single-leg device were simulated as a function of the current and the height ratio via the finite element method 43 . The total height of the single-leg was set as 9 mm, where the height ratio of (Bi,Sb) 2 Te 3 to GeTe was defined as x /(1− x ).…”

Rational design from materials to devices enables an efficiency of 10.5% based on thermoelectric (Bi, Sb)2Te3 and Mg3(Bi, Sb)2 for power generation

“…[17][18][19] Due to its excellent TE performance in the low temperature region, BST is often used as the low-temperature part of segmented devices to obtain high efficiency at large temperature differences. [20][21][22][23] For example, Hu et al demonstrated an efficiency of B11% under a DT of 590 K in a segmented Bi 2 Te 3 /PbTe module. 23 Zhang et al reported a high efficiency of up to 12% in a Bi 2 Te 3 /SKD segmented module under a temperature difference of 541 K. 20 Although existing segmented devices have achieved high efficiency, they are all obtained at high hot-side temperatures and their efficiency within the temperature range of low-grade waste heat recovery is not competitive.…”

Grain boundary re-crystallization and sub-nano regions leading to high plateau figure of merit for Bi2Te3 nanoflakes

“…The foundation of thermoelectric technology is thermoelectric materials, which can realize direct and reversible energy conversion between heat and electricity. [6][7][8] As an energy conversion technology, thermoelectric conversion efficiency (Z) 9,10 is typically considered to be the most important performance indicator. The Z is dominated by the dimensionless figure of merit (zT) of thermoelectric materials, 11,12 defined as zT = S 2 sT/k, where S is the Seebeck coefficient, s is the electrical conductivity, T is the absolute temperature, and k is the total thermal conductivity.…”