Exploration and Optimization of Tellurium‐Based Thermoelectrics

Historically, thermoelectric materials have been most naturally paired with spacecrafts such as
Voyager I and II, which were launched in 1977 and are still functional to‐date with an average efficiency
(Equation 1.2) of ~8 %. These materials work so well, they have been included in Mars Landers, Ulysses,
Galileo, Cassini, and Apollo missions. TE materials are ideal in these deep‐space applications; the barren
cold of outer space combined with the constant radioactive decay of the PuO2 fuel, creates an ideal
temperature gradient for thermopower. [32] Of the aforementioned materials, Bi2Te3, PbTe, SiGe, and
TAGS have all been implemented in space travel missions. [14, 23, 33] Materials are installed in a
radioisotope thermoelectric generator (RTG) which uses high‐energy radioactive fuel to generate heat
such as 238 Pu in the form of PuO2. As the fuel creates heat, it is transferred to thermocouples, moving
into the TE modules which are also connected to a heat sink. The electricity is collected and then used
by the craft similar to a typical battery’s use. This generator is shown conceptually in Figure 1.4 (a):
Figure 1.4 (a) RTG [32] (b) Automotive generator [34]
Cooling devices use an array of Peltier couples similar to Figure 1.3, all connected in series. As
batteries or other current sources can be utilized to drive high‐temperature electrons (or holes) away
from the cold end of the couples, heat is transported towards the opposite side of the device. [35] If this
particular side of the device is outside of a closed system, such as an insulated vessel, then the heat is
drawn out into the surroundings. Thus an electric refrigerator is created where electrons serve as
coolants! Thanks to the Peltier Effect, manufacturers have produced thermoelectric refrigerators for
the inside of cars [36] to run on a 12V DC automotive adapter or those of similar size and functionality to
that of bar fridges (38 L). These types of refrigerators are capable of cooling to about 288 K with almost
no noise or vibration (excluding of course, the in‐car cooler) and carry only the weight of the device
casing. [37] Unfortunately, for a thermoelectric refrigerator to rival that of a typical compressor‐based
home refrigerator, one would need a 9.2; the current market thermoelectrics have only recently
broken 1.0. [38] That being said, a 2 would yield practical applications for home and
commercial heating/cooling. Other potential applications for these types of devices are in‐car climate‐
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