We analyse the possibilities opened by nanostructuring for the efficient use of silicon as a thermoelectric material. Nanostructured silicon does not offer significant opportunities from the point of view of an increased Seebeck coefficient; however, nanostructuring allows an important advantage in terms of the reduction of thermal conductivity, which is a key factor for increasing the thermoelectric figure of merit. We will show that when the phonon contribution to the thermal conductivity is reduced down to the order of (or below) 1 W/(mK), doping of silicon can be tailored to optimize the figure of merit. In particular, the figure of merit can increase by more than a factor of two if the doping concentration varies by an order of magnitude. We report the numerical calculation of the efficiency for a thermoelectric generator based on silicon nanowires, taking into account the dependence of thermoelectric parameters on temperature. Finally, we show that, for a given thermal conductivity, the optimal doping concentration depends on the nanowire width and on the temperature difference between the hot and cold sources.
Optimization of the thermoelectric properties of nanostructured silicon
PENNELLI, GIOVANNI;MACUCCI, MASSIMO
2013-01-01
Abstract
We analyse the possibilities opened by nanostructuring for the efficient use of silicon as a thermoelectric material. Nanostructured silicon does not offer significant opportunities from the point of view of an increased Seebeck coefficient; however, nanostructuring allows an important advantage in terms of the reduction of thermal conductivity, which is a key factor for increasing the thermoelectric figure of merit. We will show that when the phonon contribution to the thermal conductivity is reduced down to the order of (or below) 1 W/(mK), doping of silicon can be tailored to optimize the figure of merit. In particular, the figure of merit can increase by more than a factor of two if the doping concentration varies by an order of magnitude. We report the numerical calculation of the efficiency for a thermoelectric generator based on silicon nanowires, taking into account the dependence of thermoelectric parameters on temperature. Finally, we show that, for a given thermal conductivity, the optimal doping concentration depends on the nanowire width and on the temperature difference between the hot and cold sources.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.