Measurement of thermoelectric properties of phenylacetylene-capped silicon nanoparticles and their potential in fabrication of thermoelectric materials

Silicon is a highly attractive material for the fabrication of thermoelectric materials. Nanostructured silicon materials, such as silicon nanowires (SiNWs), show great potential as they show low thermal conductivities due to efficient phonon scattering but similar electrical conductivities to bulk silicon. Silicon nanoparticles (SiNPs) are easier to synthesize and show a greater number of surface defects, which suggests that more efficient phonon scattering can be achieved, but these materials also show low electrical conductivity due to defects within the materials unless pressed at high temperatures (1100°C). Conjugated capping layers show the potential to bridge these defects, giving higher conductivity without the need for this process. Phenylacetylene-capped SiNPs are synthesized via the micelle reduction method and pressed into a pellet. Measurements of the electrical conductivity, Seebeck coefficient, and thermal conductivity were taken. The results show that the material produced from these particles shows a relatively high Seebeck coefficient (3228.84 μV K−1) which would have a positive effect on the figure of merit (ZT). A respectable electrical conductivity (18.1 S m−1) and a low thermal conductivity (0.1 W m−1 K−1) confirm the potential of using conjugated molecules as a way of cross-linking between nanoparticles in a bulk material fabricated from SiNPs. These results give a figure of merit of 0.57, which is comparable to better established thermoelectric materials.