Influences of different barrier films on microstructures and electrical properties of Bi2Te3-based joints

Diffusion barrier film was strongly proposed to utilize in Bi₂Te₃-based thermoelectric (TE) module. However, effects of different barriers on microstructures of solder joints and electrical properties of TE modules were still unclear, which were vital in practical applications. In current work, Bi₂Te₃-based TE modules without barrier (TM), with Ni (TM_Ni) and with Ni/Au (TM_Ni/Au) were fabricated via reflow-soldering. Experimental results revealed that at the interface between SAC305 solder and P- or N- type Bi₂Te₃ sample, the Ni or Ni/Au barrier could efficiently inhibit severe growth of the intermetallic compound (IMC) phase. Remarkably, a thinner IMC layer was observed at the solder/Au/Ni/Bi₂Te₃ interface, which was attributed to effects of Au elements on suppressing the formation of IMCs. The results of power generation ability test revealed that TM_Ni exhibited higher value of output power (P) under the temperature difference (ΔT) due to its higher values of open circuit voltage (V) and output current (I). On the other hand, since the lowest electrical resistance (R) and relatively low output current of TM_Ni/Au were measured during the test, the TM_Ni/Au was suggested to generate less heat, meaning it consumed less energy, and hence be theoretically more efficient in improving the conversion efficiency.