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Page 6 of 21 Chen et al. Energy Mater. 2025, 5, 500120 https://dx.doi.org/10.20517/energymater.2024.311

Bi Te using RF magnetron sputtering technique are 285 °C temperature of annealing and 103.5 sccm flow
3
2
rate of Ar. However, the TE properties of stoichiometric Bi Te films using this press have been poor, and
3
2
further optimization of additional deposition parameters (for example, annealing and substrate
temperatures) has been proposed. Furthermore, in the study of Khumtong et al., the RSM based on CCD
has been employed to optimize thin films of Sb Te deposition using the RF magnetron sputtering
2
3
[37]
technique . It has been found that the highest TE power factor of Sb Te thin films requires deposition
2
3
parameters Ar gas flow rate 120 sccm and processing temperature 375 °C. The highest power factor value
obtained for stoichiometric Sb Te film is 2.0 × 10 W/mK at 250 °C.
2
-3
3
2
Carbon materials are widely studied in electronic devices due to their availability in different structures .
[38]
The high electrical conductivity is crucial for TE performance enhancement. Jagadish et al. developed a
DOE study on the investigation of TE properties of thin films of Bi Te on recycled carbon fiber by
2
3
electrodeposition technique . Herein, the DOE based on the D-optimal model under RSM has been
[39]
adopted to optimize the combined effect of electrodeposition parameters, leading to the optimum Seebeck
coefficient. The authors used a multivariate approach involving DOE based on 23 runs to optimize
experimental parameters. The optimum electrodeposition parameters are potential -0.10 V, time 0.5 h,
temperature 25 °C, and electrolyte compositions 0.240 Bi/(Bi + Te). Thus, using DOE, the optimized
electrodeposition parameters yielded an experimental Seebeck coefficient of -13.42 μV/K, about 33% larger
than samples prepared without DOE.
Lead chalcogenides (PbTe, PbSe, PbS) are excellent TE materials. In particular, Pb Sn Te-based materials
x
1-x
are promising for TE applications due to their high ZT values. Recently, Sam et al. have developed a DOE
method for synthesizing Pb Sn Te (x = 0.67) crystals by horizontal vapor phase growth method . This
[40]
1-x
x
study employs 2 full factorial design to correlate ZT with the effect of synthesis temperature and time.
k
Based on the ANOVA of ZT, the synthesis temperature and time exhibit significant ZT response. Thus, the
crystals prepared at 1,200 °C for 4 h have exhibited the highest ZT of approximately 0.084.
Due to high operating temperatures, SiGe alloy-based TE materials are widely used in radioisotope TEGs .
[41]
[42]
The n-type SiGe alloy may exhibit a very high ZT value of 1.84 at 1,073 K . Ahmad et al. studied statistical
DOE and RSM optimization of ball milling and hot press sintering parameters to prepare SiGe alloy . In
[43]
this study for TE properties of SiGe alloy, 13 experiments were incorporated in two-factor CCD for
obtaining regression equations. For the maximum ZT, the hot press temperature is 1,504.5 K, and the time
for ball milling is 53.6 h. Herein, the predicted and experimental optimum ZT values were 1.148 and 1.146,
respectively.

Effective heating and cooling on the surface of TEG increases the temperature difference across TEG, which
directly relates to device efficiency and output power. However, the construction of the microstructure of
TE materials is vital to withstand significant temperature differences for performance enhancement. The
optimization of TE legs (such as the areas of hot and cold sides, pin configuration, contact angle, etc.) and
the construction of the 3D architecture of TE legs tailors to avoid the brittleness of material and the heat
stagnation in its legs . Maduabuchi studied thermomechanical optimization using a deep neural
[45]
[44]
network (DNN). The data obtained from the finite element method was fed to the DNN to learn the
pattern. The well-fitting of experimental and DNN results indicated the suitability of DNN, reducing the
simulation time. The temperature difference between the hot and cold sides was crucial to maximize the
output power. Besides, this report discussed the optimization of temperature effect on temperature on the
hot side (T ) and temperature on the cold side (T ) by the wind speed. This effective cooling was achieved
h
c
by installing low thermal conductivity material on the cold side, and the cold side temperature was