Achieving 12.7% energy conversion efficiency in segmented GeTe/BST-SKD thermoelectric modules via broad-temperature and structural optimizations

Abstract

Solid-state thermoelectric (TE) power generation through the direct conversion of a temperature difference into electricity has received worldwide attention. In this work, a segmented GeTe/BST-SKD TE module is optimized and fabricated to achieve outstanding power density and energy conversion efficiency. To enable high module-level TE performance, p-type GeTe with a ZT_max of 2.47 is used, while p-type BST (Bi_2−xSb_xTe₃, with high ZT in the low temperature range) and n-type SKD (skutterudite, Yb_0.3Co₄Sb₁₂) are optimized to reach ZT_max values of 1.38 and 1.33, respectively. Furthermore, module structure optimization is conducted using multiphysics-field simulations for three shape factors, including the segmentation ratio, height-to-area ratio, and cross-sectional area ratio between p- and n-type legs. When the three factors are 0.35, 0.67 mm⁻¹, and 1.85, respectively, both the maximum power density and energy conversion efficiency reach their optimal values. Finally, Ni foil is applied at the GeTe/BST interface to serve as both a metallization layer and a diffusion barrier, minimizing internal contact resistances and enhancing high-temperature stability. The maximum power density and energy conversion efficiency of the segmented module are increased by 35% and 21%, respectively, compared with those of the unsegmented one. The segmented module achieves a substantial power output of ~0.43 W at ΔT = 500 K, corresponding to a power density of 0.35 W/cm² per module area and 143 W kg⁻¹ per module weight, with an effective material-level power density of 1.51 W/cm². The segmented module achieves an outstanding energy conversion efficiency of 12.7%, demonstrating the effectiveness of the optimized leg-segmentation strategy for high-performance solid-state energy harvesting.

Graphical abstract

Keywords

thermoelectrics (TEs) / segmented module / structure optimization / power density / energy conversion efficiency

References

[1] Zhang Y R , Feng J Q , Li L J . et al. Integrated direct air CO₂ capture and utilization via in-situ catalytic conversion to fuels and chemicals using dual functional materials: Recent progresses and perspectives. Frontiers in Energy, 2025, 19(5): 586–598

[2] Liu F P , Wang Y H , Lang X M . et al. Fundamentals and economic analysis of hydrate-based carbon dioxide sequestration. Carbon Neutrality, 2025, 4(1): 19

[3] Shen W Z , Zhao Y X , Liu F . Highlights of mainstream solar cell efficiencies in 2024. Frontiers in Energy, 2025, 19(1): 8–17

[4] Zhao W W , Lin X F , Zhang T T . et al. Large-scale energy storage for carbon neutrality: Thermal energy storage for electrical vehicles. Carbon Neutrality, 2024, 3(1): 30

[5] Li A , Anand R S , Huang W B . et al. Performance enhancement, economic analysis, and futuristic insight of single-well medium-deep and deep geothermal systems. Frontiers in Energy, 2025, 19(1): 33–58

[6] Wang L , Zhang W H , Wang C B . et al. Solar-powered integrated thermoelectric system for simultaneous electricity and freshwater production with salt and brine recovery. Interdisciplinary Materials, 2026, 5(2): 301–313

[7] Palaporn D , Tanusilp S A , Sun Y F . et al. Thermoelectric materials for space explorations. Materials Advances, 2024, 5(13): 5351–5364

[8] Zhao K , Liu C , Shao T . et al. Enhanced thermoelectric performance of Bi₂Te₃ by carbon nanotubes and silicate aerogel co-doping toward ocean energy harvesting. Materials Today Sustainability, 2023, 23: 100476

[9] Jaziri N , Boughamoura A , Müller J . et al. A comprehensive review of Thermoelectric Generators: Technologies and common applications. Energy Reports, 2020, 6(S7): 264–287

[10] Yang K Y , Li X Y , Jiang Y X . et al. General screening rules and segmented optimization strategy for efficient thermoelectric devices validated by Mg₃(Sb,Bi)₂/Bi_0.5Sb_1.5Te₃-GeTe module. Advanced Science, 2025, 12(27): 2502832

[11] Yin Y S , Lin S C , Xu Z Y . et al. Giant-thermopower ionogels for multifunctional energy harvesting through molecularly selective ionic pairing and hydrogen bonding. The Innovation Energy, 2024, 1(4): 100048

[12] Ahmadian-Yazdi M R , Lin S C , Cai Z L . Unveiling heavy heterovalent doping-modulated microstructure and thermoelectric performance in bulk hybrid perovskite single crystals. Chemical Engineering Journal, 2024, 487: 150477

[13] Yan L F , Zhao L L , Yang G T . et al. High performance solid-state thermoelectric energy conversion via inorganic metal halide perovskites under tailored mechanical deformation. Frontiers in Energy, 2022, 16(4): 581–594

[14] Lv S , Qian Z Q , Hu D Y . et al. A comprehensive review of strategies and approaches for enhancing the performance of thermoelectric module. Energies, 2020, 13(12): 3142

[15] Xie L , Ming C , Song Q F . et al. Lead-free and scalable GeTe-based thermoelectric module with an efficiency of 12%. Science Advances, 2023, 9(27): eadg7919

[16] Jin Y , Qiu Y T , Pan C F . et al. Advanced GeTe-based thermoelectrics: Charting the path from performance optimization to devices. Advanced Materials, 2025, 37(24): 2500802

[17] Mei Q C , Liao C Y , Xu W B . et al. Mn-alloying induced thermoelectric performance enhancement in GeTe through synergistic band engineering and lattice modulation. Materials Today Energy, 2025, 53: 101972

[18] Zhu J L , Li R H , Tan X B . et al. Valence band modification and enhanced phonon-phonon interactions for high thermoelectric performance in GeTe. Advanced Functional Materials, 2025, 35(11): 2417260

[19] Lee K H , Kim S I , Kim H S . et al. Band convergence in thermoelectric materials: Theoretical background and consideration on Bi–Sb–Te alloys. ACS Applied Energy Materials, 2020, 3(3): 2214–2223

[20] Wang S Y , Sun Y X , Yang J . et al. High thermoelectric performance in Te-free (Bi,Sb)₂Se₃ via structural transition induced band convergence and chemical bond softening. Energy & Environmental Science, 2016, 9(11): 3436–3447

[21] Chen K Y , Sun Q Q , Li H T . et al. Grain boundary strengthening achieves extraordinary module efficiency in GeTe-based thermoelectric materials. Small, 2025, 21(21): 2502510

[22] Xie L , Liu R H , Zhu C X . et al. Enhanced thermoelectric performance in Ge_0.955–xSb_xTe/FeGe₂ composites enabled by hierarchical defects. Small, 2021, 17(25): 2100915

[23] Gahtori B , Bathula S , Tyagi K . et al. Giant enhancement in thermoelectric performance of copper selenide by incorporation of different nanoscale dimensional defect features. Nano Energy, 2015, 13: 36–46

[24] Wu G , Zhang Q , Tan X J . et al. Bi₂Te₃-based thermoelectric modules for efficient and reliable low-grade heat recovery. Advanced Materials, 2024, 36(26): 2400285

[25] Du J Y , Sun Y X , Guo F K . et al. Enhanced thermoelectric cooling performance of (Bi, Sb)₂Te₃ through platinum doping. Materials Today Physics, 2025, 53: 101705

[26] Li Y C , Bai S L , Wen Y . et al. Realizing high-efficiency thermoelectric module by suppressing donor-like effect and improving preferred orientation in n-type Bi₂(Te, Se)₃. Science Bulletin, 2024, 69(11): 1728–1737

[27] Zhang W , Song H D , Jiang L F . et al. Symmetry-guided crystal structure design enhances average ZT and mechanical properties in rhombohedral GeTe. Materials Today Physics, 2025, 58: 101863

[28] Xu F , Liu B , Ang R . Advancing thermoelectrics in lead-free rhombohedral GeTe via interfacial engineering with MXene. Advanced Energy Materials, 2025, 15(21): 2405554

[29] Jiang B B , Wang W , Liu S X . et al. High figure-of-merit and power generation in high-entropy GeTe-based thermoelectrics. Science, 2022, 377(6602): 208–213

[30] Fu G , Lin S C , Liu Y X . et al. Synergistic strategy via modulated energy filtering and hierarchical defects evolution for high performance GeTe thermoelectrics. Chemical Engineering Journal, 2024, 498: 155652

[31] Zhao L D , Lo S H , Zhang Y S . et al. Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals. Nature, 2014, 508(7496): 373–377

[32] Zhao L D , Tan G J , Hao S Q . et al. Ultrahigh power factor and thermoelectric performance in hole-doped single-crystal SnSe. Science, 2016, 351(6269): 141–144

[33] Li K , Sun L , Bai W . et al. High-entropy strategy to achieve electronic band convergence for high-performance thermoelectrics. Journal of the American Chemical Society, 2024, 146(20): 14318–14327

[34] Xu L Q , Xiao Y , Wang S N . et al. Dense dislocations enable high-performance PbSe thermoelectric at low-medium temperatures. Nature Communications, 2022, 13(1): 6449

[35] Jiang B B , Yu Y , Cui J . et al. High-entropy-stabilized chalcogenides with high thermoelectric performance. Science, 2021, 371(6531): 830–834

[36] Li D , Shi X L , Feng Z Y . et al. Fast fabrication of high-performance CoSb₃-based thermoelectric skutterudites via one-step Yb-promoted peritectic solidification. Advanced Functional Materials, 2023, 33(46): 2305269

[37] Chu J , Huang J , Liu R H . et al. Electrode interface optimization advances conversion efficiency and stability of thermoelectric devices. Nature Communications, 2020, 11(1): 2723

[38] Li W J , Ghosh S , Liu N . et al. Half-Heusler thermoelectrics: Advances from materials fundamental to device engineering. Joule, 2024, 8(5): 1274–1311

[39] Zhu H T , Li W J , Nozariasbmarz A . et al. Half-Heusler alloys as emerging high power density thermoelectric cooling materials. Nature Communications, 2023, 14(1): 3300

[40] Zhang X Y , Bu Z L , Lin S Q . et al. GeTe thermoelectrics. Joule, 2020, 4(5): 986–1003

[41] Xing T , Song Q F , Qiu P F . et al. High efficiency GeTe-based materials and modules for thermoelectric power generation. Energy & Environmental Science, 2021, 14(2): 995–1003

[42] Zhang T D , Deng S P , Zhao X D . et al. Regulation of Ge vacancies through Sm doping resulting in superior thermoelectric performance in GeTe. Journal of Materials Chemistry A, 2022, 10(7): 3698–3709

[43] Chen S , Bai H , Li J J . et al. Vacancy-based defect regulation for high thermoelectric performance in Ge₉Sb₂Te_12–x compounds. ACS Applied Materials & Interfaces, 2020, 12(17): 19664–19673

[44] Wang Z R , Wu H , Zhang B . et al. Phase modulation enabled high thermoelectric performance in polycrystalline GeSe_0.75Te_0.25. Advanced Functional Materials, 2022, 32(26): 2111238

[45] Pei J , Shi J L , Li H Z . et al. Design and fabrication of segmented GeTe/(Bi,Sb)₂Te₃ thermoelectric module with enhanced conversion efficiency. Advanced Functional Materials, 2023, 33(20): 2214771

[46] Bu Z L , Zhang X Y , Shan B . et al. Realizing a 14% single-leg thermoelectric efficiency in GeTe alloys. Science Advances, 2021, 7(19): eabf2738

[47] Bu Z L , Zhang X Y , Hu Y X . et al. An over 10% module efficiency obtained using non-Bi₂Te₃ thermoelectric materials for recovering heat of < 600 K. Energy & Environmental Science, 2021, 14(12): 6506–6513

[48] Zhong J X , Yang X Y , Lyu T . et al. Nuanced dilute doping strategy enables high-performance GeTe thermoelectrics. Science Bulletin, 2024, 69(8): 1037–1049

[49] Qi X , Kang T , Yang L . et al. Simultaneous suppression of phonon transport and carrier concentration for efficient rhombohedral GeTe thermoelectric. Advanced Science, 2024, 11(47): 2407413

[50] Guo Z , Wu G J , Yuan M H . et al. High thermoelectric performance and energy conversion in Hg-doped GeTe. Advanced Functional Materials, 2025, 35(17): 2419431

[51] Gu M , Bai S Q , Wu J H . et al. A high-throughput strategy to screen interfacial diffusion barrier materials for thermoelectric modules. Journal of Materials Research, 2019, 34(7): 1179–1187

[52] Zhang Q H , Huang X Y , Bai S Q . et al. Thermoelectric devices for power generation: Recent progress and future challenges. Advanced Engineering Materials, 2016, 18(2): 194–213

[53] Park J M , Hyeon D Y , Ma H S . et al. Enhanced output power of thermoelectric modules with reduced contact resistance by adopting the optimized Ni diffusion barrier layer. Journal of Alloys and Compounds, 2021, 884: 161119

[54] Li J Q , Zhao S Y , Chen J L . et al. Al–Si alloy as a diffusion barrier for GeTe-based thermoelectric legs with high interfacial reliability and mechanical strength. ACS Applied Materials & Interfaces, 2020, 12(16): 18562–18569

[55] Duan Y L , Lin S C , Bai Y F . et al. Experiment-Validated multiphysics modeling, generalizable deep learning and interpretable global sensitivity analyses for thermoelectric generators. International Journal of Heat and Mass Transfer, 2024, 229: 125711

[56] Li Z L , Yang X F , Wang Q . et al. Bi_2–xSb_xTe₃ thermoelectric composites with high average zT values: From materials to devices. Materials Lab, 2022, 1: 220026

[57] Wang D Z , Liu W D , Mao Y Q . et al. Decoupling carrier-phonon scattering boosts the thermoelectric performance of n-type GeTe-based materials. Journal of the American Chemical Society, 2024, 146(2): 1681–1689

[58] Wu X Z , Wang L Q , Li A R . et al. High conversion efficiency in intrinsic high power-density Mg₂Sn-GeTe thermoelectric generator. Advanced Science, 2025, 12(40): e06997

[59] Lu X F , Zhang Q H , Liao J C . et al. High-efficiency thermoelectric power generation enabled by homogeneous incorporation of MXene in (Bi,Sb)₂Te₃ matrix. Advanced Energy Materials, 2020, 10(2): 1902986

[60] Shi W J , Qin D D , Sun Y X . et al. Batch fabrication and interface stabilization accelerate application of skutterudite thermoelectric module for power generation. Advanced Energy Materials, 2024, 14(12): 2303698

[61] Nie G , Suzuki S , Tomida T . et al. Performance of skutterudite-based modules. Journal of Electronic Materials, 2017, 46(5): 2640–2644

[62] Hu X K , Jood P , Ohta M . et al. Power generation from nanostructured PbTe-based thermoelectrics: Comprehensive development from materials to modules. Energy & Environmental Science, 2016, 9(2): 517–529

[63] Fu C G , Bai S Q , Liu Y T . et al. Realizing high figure of merit in heavy-band p-type half-Heusler thermoelectric materials. Nature Communications, 2015, 6(1): 8144

[64] Yu J J , Xing Y F , Hu C L . et al. Half-Heusler thermoelectric module with high conversion efficiency and high power density. Advanced Energy Materials, 2020, 10(25): 2000888

[65] Li W J , Poudel B , Kishore R A . et al. Toward high conversion efficiency of thermoelectric modules through synergistical optimization of layered materials. Advanced Materials, 2023, 35(20): 2210407

[66] Liu S X , Wang W , Xie L . et al. Realizing high thermoelectric performance in GeTe-based alloys without lead addition. Advanced Functional Materials, 2026, 36(5): e10362

[67] Zhang C H , Jin K P , Dong H L . et al. Synergistic enhancement of thermoelectric performance of n-type PbTe by resonant level and single-atom-layer vacancies. Nano Energy, 2024, 126: 109615

[68] Jayachandran B , Dasgupta T , Singh A . A constant properties model for the performance estimation in segmented thermoelectric generator elements and its experimental validation using an n-type Mg₂Si_0.3Sn_0.7–Bi₂Te_2.7Se_0.3 segmented leg. Acs Applied Energy Materials, 2023, 6(11): 6157–6170

[69] Xu C C , Liang Z X , Ren W Y . et al. Realizing high energy conversion efficiency in a novel segmented-Mg₃(Sb, Bi)₂/Cubic-GeTe thermoelectric module for power generation. Advanced Energy Materials, 2022, 12(45): 2202392

[70] Wang M , Zhang Q , Pang K K . et al. Robust homogeneous segmented power generator driven by Sb₂Te₃-based thermoelectrics. Advanced Materials, 2025, 37(24): 2503128

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