بهبود بازده تبدیل انرژی حالت جامد با استفاده از نانوساختارهای ترموالکتریک

Solid-state energy conversion technologies such as thermoelectric refrigeration and power generation require materials with low thermal conductivity yet high electrical conductivity and Seebeck coefficiency. Although semiconductors are the best thermoelectric materials, they rarely have the such features. Nanostructures such as superlattices, quantum wires, and quantum dots provide novel methods to improve the solid-state energy conversion efficiency through electron and phonon transport engineering. In this research, a semiconducting superlattice, consisting of periodic nano layers of silicon and germanium, has been studied. Due to nano scale effects, conductive heat transfer does not satisfy Fourier's law of thermal conduction. The equation of phonon radiative transfer has been solved numerically. The results show that the thermal conductivity of the nano structure is much lower than the macro structures with the same aspect ratio. It is also noticed that with the constancy in the ratio of layers’ thickness, further reduction in layers’ thickness leads to more temperature jump at interfaces and consequently further reduction in effective thermal conductivity which finally improves the thermoelectric properties. The findings show that the effective thermal conductivity depends on the density of interfaces per unit length.