Enhanced Seebeck coefficient in silicon nanowires containing dislocations

In recent years, research on thermoelectric (TE) materials has intensified - thanks to the exciting potential of low-dimensional structures such as nanowires. Experiments have shown that nano-structuring materials can greatly reduce their thermal transport properties, significantly enhancing thermoelectric performance. With reduced thermal conductivity, nano-structured silicon - which is plentiful and low-cost - becomes a competitive TE material, but still trails traditional TE materials in overall performance. In this study, we show that the creation of extended defects within the crystal structure of silicon nanowires can create an additional enhancement. Relative to regular silicon nanowires, extended defects lead to an increased Seebeck coefficient. The effect is a consequence of the creation of dislocations and dislocation-loops, intentionally introduced in the nanowires. These defects create nano-scale potential barriers which theoretical studies have predicted can enhance silicon's thermopower by energy filtering of low-energy carriers. Although the defects slightly reduce carrier mobility - increasing electrical resistivity in the nanowires - their presence creates an overall two-fold enhancement in the thermoelectric power factor.