Wednesday, 4 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
The conversion efficiency of thermoelectric (TE) devices is determined by the dimensionless figure of merit ZT, which is expressed as ZT = S2σT/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the absolute temperature, respectively. The key strategy to enhance ZT is through decreasing the thermal conductivity of thermoelectric materials. In this study, finite element analysis was used to investigate the effect of stripe-patterned Si substrates on thermal properties of a thermoelectric thermoelement, which consists of PbSe and PbTe thin film layers grown on the periodic patterned Si substrates. The width and depth of the stripe patterns were varied from 10 µm to 0.5 µm to determine their effects on the heat transport in the thermoelement. The calculated results reveal that the depth and width of the stripe patterns play an important role in decreasing the thermal conductivity of the thermoelectric module. The effect of the dimension of the patterns on the effective thermal conductivity of the TE thermoelement was shown in figure 1. The thermal conductivity is lower with respect to the deeper and narrower stripe patterns. The decreased thermal conductivity results from the enhanced phonon-boundary scattering due to the presence of periodic patterns. The phonons can be scattered more extensively when the dimension of the patterns is comparable to the mean free path of TE materials. Therefore, we modeled a thermoelectric generator (TEG) composed of stripe-patterned TE thermoelements taking advantage of its lower thermal conductivity. The dimension of the patterns was optimized selected to generate to achieve a higher power output of TEG. This work demonstrated the feasibility of using nanopatterned thermoelectric (TE) thermoelements to improve TE generator performance.