Thermoelectric performance of granular semiconductors

TL;DR

This paper investigates the thermoelectric properties of granular semiconductors with weak intergrain coupling, analyzing how doping and grain size influence thermopower and efficiency, and identifying conditions for optimized thermoelectric performance.

Contribution

It provides a theoretical analysis of thermoelectric performance in granular semiconductors considering doping effects and grain size, highlighting potential for high figure of merit values.

Findings

Optimal grain size around 5nm for high figure of merit

Figure of merit can exceed one in certain conditions

Thermopower remains finite in compensated semiconductors

Abstract

We study thermoelectric properties of granular semiconductors with weak tunneling conductance between the grains, g_t < 1. We calculate the thermopower and figure of merit taking into account the shift of the chemical potential and the asymmetry of the density of states in the vicinity of the Fermi surface due to n- or p-type doping in the Efros-Shklovskii regime for temperatures less than the charging energy. We show that for weakly coupled semiconducting grains the figure of merit is optimized for grain sizes of order 5nm for typical materials and its values can be larger than one. We also study the case of compensated granular semiconductors and show that in this case the thermopower can be still finite, although two to three orders of magnitude smaller than in the uncompensated regime.