Preparation And Properties Of Polymer/Inorganic Thermoelectric Composites Based On Polythiophene And Polyfluorene Derivatives

Polymer thermoelectric(TE) materials that highlight the advantage of abundant source, low price, easy synthesis at low temperature, low thermal conductivity and structural design, have received more and more attention in recent years. Traditional polymer TE materials, such as polyaniline(PANI), polypyrrole(PPY), polythiophene(PTh), poly(3,4-ethylenedioxythiophene)(PEDOT), have been already studied maturely, however polymers with novel structure(such as donor-acceptor, abbreviated as D-A) which have promising TE properties have attracted great attentions in the field of conducting polymers though the reported examples are very limited. The conversion efficiency between heat and electricity for traditional TE polymers is still very low, and their TE properties are generally improved by doping with inorganic materials. Since doping is very limited to improve TE properties of conducting polymers, in order to improve the TE performance of conducting polymers to meet the practical applications, researchers have to take other methods such as tuning the molecule sructure of polymers. Based on the above-mentioned background, in this thesis, we have(1) studied the TE properties of PTh composites,(2) designed and synthesized a series of conjugated polymers containing D-A structure, and(3) studied their TE properties by preparing polymer/inorganic composites with conducting fillers(graphite and multi-walled carbon nanotubes, abbreviated as G and SWNT respectively). The detailed contents and results are describing as follows:1. Prepare composites based on traditional TE materials, trying to improve the TE properties.(1) PTh, Bi2Te3 and G have a comprehensive influence on the TE properties of Bi2Te3/G/PTh composites: with increasing G content, the electrical conductivity(?) of the composites increased dramatically, while the Seebeck coefficient(S) decreased; the addition of Bi2Te3 is helpful to improve S to some extent, while a further increased addition can decrease both S and ?; PTh helps keep a relatively low thermal conductivity(?) of this composites.(2) Spark plasma sintering(SPS) makes the structure of composites denser, and helps increase S while decrease ?.(3) As a result of different components and preparation methods, sample G75B5-S(5%Bi2Te3/75%G/PTh, prepared by SPS under a vacuum of 1.5�10-3 Pa, at 40 Mpa and 250 �C) has obtained the highest ZT(3.3�10-3).2. Designed and synthesized a novel polymer TE material with D-A structure. D-A conjugated polymer F8 BT has relatively high carrier mobility due to the ordered packing and regular arrangement of its polymer chains. After Fe Cl3-doping, a high carrier concentration was introduced, so the electrical conductivity was highly increased. On the other hand, during the doping process, the conformation and arrangement of F8 BT chains could be changed even become flummoxed, so the carrier mobility has decreased. As a result, the Seebeck coefficient of Fe Cl3-doping F8 BT was decreased. Finally, the F8BT-Fe Cl3/SWNT composites obtained its highest ZT value of 7.1�10-4, 54% higher than that of F8BT/SWNT composites, which is 4.6�10-4. The result for F8BT/G composites is also similar. And the highest power factor and ZT value for F8BT-Fe Cl3/80%G composite are 4.9 ?W/m K2 and 8.0�10-4,respectively, which are much higher than that of corresponding F8BT-Fe Cl3/80%SWNT composites.