熱電材料為一種能將熱能與電能互相轉換的綠色能源材料，以其所製成的熱電元件無噪音且反應快速，可用於廢熱回收及局部致冷等應用。傳統的熱電模組有兩種，包含塊材以及薄膜模組，然而高成本、耗時以及厚度限制為此二者的缺點。因此，具有低成本、可大量生產且可微型化等優點的印刷式熱電厚膜模組在近幾年被提出並且被大量研究。然而因其添加了黏著劑而造成的不良電性質一直是亟需改善的問題。雖然高溫退火製程可以提升厚膜的電導率以達更好的熱電表現，但高溫製程不適用於以可撓高分子為基板的厚膜。 因此，本研究在相對低溫下以電流輔助燒結製程在可撓高分子基板上製備高效能鉍-銻-碲系熱電厚膜。相較於純熱壓之試片，等溫下熱壓通電流的試片的導電率提升了兩倍，包括較高的載子遷移率 (163  3 cm/V∙s)以及較低的電阻率 (2.9  0.1 mΩ∙cm)，也因此具有顯著提升的功率因子 (1.95  0.05 mW/mK2)。此外，我們也將透過理論模型來分析並評估不同的電流密度、電流模式以及燒結溫度對微結構、缺陷機制、散射機制及熱電性質的影響。

Thermoelectric generation devices are able to convert waste heat into electricity. Typical thermoelectric modules, including bulk and thin-film modules, have the drawbacks of high cost, lengthening process and the narrow range of achievable thickness. Recently, printed thick-film thermoelectrics have been proposed for their virtues of miniaturization, low cost and mass production. However, the poor electrical property of thick films, mainly due to residual binders, has long been an issue. Although a high-temperature annealing can improve the electrical conductivity of films, the high temperature might exceed the glass transition point (Tg) of the flexible polymer-based substrate and limit the substrate selectivity. In this study, we presented a low-temperature current-assisted sintering approach to prepare high-performance Bi-Sb-Te thick films printed on polyimide substrates. Compared to the hot-pressed specimens, the electrically sintered Bi-Sb-Te thick film exhibits a 2 times enhancement of electrical property with a Hall mobility of 163  3 cm/V∙s and an electrical resistivity of 2.9  0.1 mΩ∙cm, giving rise to a large power factor of 1.95  0.05 mW/mK2. How different current density, current modes and sintering temperatures interact with microstructures, crystal defects and carrier scattering mechanism in Bi-Sb-Te films are investigated.

Abstract I
摘要 II
致謝 III
Contents V
List of figures VII
List of tables XII
Chapter 1 Introduction 1
1.1 Background information 2
1.2 Motivation 6
Chapter 2 Literature review 8
2.1 Bi-Te based compounds 8
2.1.1 Crystal structure of Bi-Te based compounds 8
2.1.2 Crystal defects in Bi-Te based compounds 10
2.2 Comparison of different thermoelectric modules 13
2.2.1 Optimized thickness of thermoelectric legs in a module 13
2.2.2 Processing of different thermoelectric modules 15
2.3 Thermoelectric thick-film materials 18
2.3.1 Applications of thermoelectric thick films 18
2.3.2 Properties of thermally-sintered Bi-Te based thick films 20
2.4 Strategy of enhancing thermoelectric transport properties of Bi-Te based films 24
2.4.1 Current-assisted sintering processes 24
2.4.2 Interfacial energy-filtering effect 30
Chapter 3 Experimental 33
3.1 Preparation of screen-printed Bi-Sb-Te thermoelectric thick films 33
3.2 Microstructure characterization 36
3.3 Thermoelectric property measurement 38
Chapter 4 Results and discussion 42
4.1 Electrically sintered Bi-Sb-Te thermoelectric thick films 42
4.1.1 Bi-Sb-Te films prepared with different current density 43
4.1.2 Bi-Sb-Te films prepared with different current mode 51
4.2 Bi-Sb-Te films electrically sintered at different temperatures 55
4.3 Theoretical modeling of the sintered Bi-Sb-Te thermoelectric thick films 67
4.3.1 Mayadas-Shatzkes model 67
4.3.2 Scattering mechanism analysis 73
Chapter 5 Conclusions 80
References 82

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