Abstract
To enhance the conversion efficiency of thermoelectric generation (TEG) devices, they must withstand larger temperature differences. Previously, a large-scale flexible TEG device was fabricated for use in energy harvesting. However, its maximum operating temperature was limited to approximately 150 °C owing to the low melting point of the Sn–Ag-based solder (∼150 °C) that bonds TE materials and electrodes. Therefore, the present study attempted to develop a bonding interface resistant to heat up to 250 °C. Ag paste was chosen as the bonding material instead of the Sn–Ag-based solder because it has many advantages such as high-temperature stability (melting point ∼ 960 °C), printability, and low electrical resistivity. Ni/Au was used as a diffusion barrier layer. Ni/Au layers were prepared by sputtering and electroplating, respectively. Investigation of the element diffusion behaviors of these two bonding interfaces at 250 °C showed that electroplated Ni blocked electrode diffusion, but Ni itself significantly diffused into n-type Bi2Te3 and formed a NiTe phase. Conversely, sputtered Ni could not block electrode diffusion, but Ni hardly diffused into n-type Bi2Te3. This work provides a fundamental understanding of the grain-boundary diffusion and diffusion properties of crystals and amorphous materials.
Published Version
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