With the development of application of wireless sensor
nodes (WSNs),
the need for energy harvesting is rapidly increasing. In this study,
we designed and fabricated a robust monolithic thermoelectric generator
(TEG) using a simple, low-energy, and low-cost device fabrication
process. Our monolithic device consists of Ag2S0.2Se0.8 and Bi0.5Sb1.5Te3 as n-type and p-type legs, respectively, while the empty space between
the legs was filled with highly dense, flexible, and thin Ag2S that serves as both an insulating spacer and a shock absorber,
which potentially augments the robustness of preventing from damage
from an external mechanical force. From the optimization of the device
structure via finite element method (FEM) simulations, a three-pair
device with dimensions of 12 mm × 10 mm × 10 mm was found
to have a theoretical maximum power density of 8.2 mW cm–2 at a ΔT of 50 K. For considering this inevitable
contact resistance, experimental measurement and FEM simulation were
combined for quantifying the junction resistance; a power density
of 2.1 mW cm–2 was established with the consideration
of the contact resistance at the p–n junctions. Using these
optimized structural parameters, a device was fabricated and was found
to have a maximum power density of 2.02 mW cm–2 at
a ΔT of 50 K, which is in good agreement with our
simulations. The results from our monolithic TEG show that despite
the simple, low-energy, and low-cost device fabrication process, the
power generation is still comparable to other reported TEGs. It is
worth mentioning that our design could be extended to other chalcogenide
materials of appropriate temperature regions and/or better zT. Besides, the quantification of contact resistance also
exhibited reference value for the enhancement of thermoelectric conversion
application. These results provide a convenient, economic, and efficient
strategy for waste energy harvesting close to room temperature, which
can broaden the applications of waste heat harvesting.