Design and fabrication of tetradymites-based vertically oriented single and multilayer thin-film thermoelectric generators

Tetradymites-based thermoelectric materials and devices have received renewed attention due to their engineering and design flexibility, large scalability, and commercial viability in producing electricity from waste heat for niche applications in small power generation and micro refrigeration. In fact, most commercially available bulk thermoelectric generators (TEGs) are made from tetradymites. In contrast to their bulk counterparts, thin-film vertical TEGs have not been widely adopted. This can be attributable to complexities in design and fabrication methodologies, device measurement challenges, and the hurdle of maintaining a large enough temperature gradient for optimal device performance. In this study, we utilize a facile approach for the design, fabrication, and characterization of tetradymite-based n-type Bi2Te3 and p-type Sb2Te3 single-layer thermoelectric generators, as well as n-type Bi2Te3/Bi2Te2.83Se0.17 and p-type Sb2Te3/Bi0.4Sb1.6Te3 alternating multilayer superlattice TEGs. State-of-the-art characterization techniques were employed to investigate the structural, chemical, and thermoelectric properties of the materials. XRD analysis showed a preferential orientation along the (100) plane with a high intensity peak at 2θ = 25.5°, and XPS spectra exhibited a high-resolution peak at 531.5 eV corresponding to the Bi 4f7/2 core level. The structural data analysis confirmed the dominant metallic phase of the materials as well as their high crystalline nature. Device characterization showed that the multilayer device performed better than the single-layer devices with a recorded voltage, power, and power density of 11 mV, 12 pW, and 15.87 mW/m3 at ΔT = 18 °C, respectively, in comparison to 9.4 mV, 7.8 pW, and 10.31 mW/m3 for the most performing single-layer devices.