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A1: Low temperature materials
Over the past 2 years silicon nanoparticles (SiNPs) functionalised with conjugated molecules have been shown to have potential as low temperature thermoelectric materials. Phenyl acetylene capped particles show ZT = 0.5 at 300 K [1] and recent theoretical work has shown the potential positive effects of polymer-semiconductor-polymer junctions on the power factor of these materials[2]. One key challenge with such materials is that of charge carriers. There are two components of organic/semiconductor nanocomposite materials in which we can introduce charge carriers; the silicon nanoparticle or the organic ligand. Recent work has shown the development of a synthetic method in which we can produce capped SiNPs with control over the charge carrier concentration in the nanoparticles using a top down approach[3]. Investigation into the effect of introducing charge carriers on the ligands via oxidation is another step toward understanding and optimising this system. Thiophene based polymers have shown to be very good organic semiconductors (e.g. PEDOT:PSS) and controlled doping these sorts of organic species are well documented[4]. As a result the synthesis of terthiophene capped SiNPs is a good starting point to investigate this. Using a previously documented method we have synthesised and characterised terthiophene capped SiNPs. Using different ratios of a variety of dopants we have investigated their effect on the power factor and how these dopants affect the long term stability of the conductivity of the materials produced.
[1] Ashby, S. P.; García-Cañadas, J.; Min, G.; Chao, Y., J. Electron. Mater., 2013, 42 (7), 1495-1498.
[2] Wang, Y.; Liu, J.; Zhou, J.; Yang, R., J Phys. Chem. C, 2013, 117 (47), 24716-24725.
[3] Ashby, S. P.; Chao, Y., J. Electron. Mater., 2013, 1-5.
[4] McCullough, R. D., Adv. Mater., 1998, 10 (2), 93-116.