Thermoelectric converter with stepwise legs for high energy conversion efficiency

Due to industrial activity, an enormous amount of heat is wasted on the environment enabling energy loss and global warming. Thermoelectric (TE) technologies make possible the direct conversion of waste heat into electrical energy. The main bottlenecks of energy conversion by TE devices are low efficiency as well as the expensive and complex fabrication procedure of industrial converters. In this work, we fabricated a Bi2Te3-based TE converter with stepwise legs for highly efficient energy conversion using a single-step sintering method. Before the fabrication of the converter, we employed the numerical simulation and found that Co is the best choice among the other well-established metallic layers, that can be used for the highly conductive covering of the nand p-type TE legs. The employment of this metal produces the lowest thermal stress that occurs in the stepwise converter at the cooling stage of a sintering process. The energy conversion efficiency of the designed converter estimated using the finite element method reaches 10.1% at a temperature difference of 375 K (Tc = 300 K). Moreover, the measured value of efficiency achieves 8.5%, which is 1.4 times higher than the commercial Bi2Te3based converters and 9-14% higher than the other reported stepwise converters. The enhanced efficiency mainly originates from the effective stepwise design of the n- and p-type TE legs. This work offers a new path for the simple single-step fabrication of the Bi2Te3-based TE converters that should have great potential for energy harvesting.