| Thermoelectric material is a function material that can realize the conversion between thermal energy and electricity.Thermoelectric materials have attracted the attention of researchers as a new sustainable development of clean energy materials.At present,the study of the inorganic thermoelectric materials are hindered due to their toxicity,difficulty in synthesis,difficulty in processing,and high price and so on,while organic thermoelectric materials with simple synthesis,easy processing,low price,and abundant raw materials,which were attracted geatly attention by reseachers.However,the research on the structure of thermoelectric materials is mainly concentrating on polyaniline,polypyrrole,polyfluorene,polythiophene and its derivatives,and other new polymers are rarely studied.Based on the above-mentioned problems,a series of polymers based on indacenodithieno[3,2-b]thiophene(IDTT)units were designed and synthesized.The relationship between the molecular structures and thermoelectric properties was systematically studied.In the end,we selected PIDTT-3T which have higher power factor to mix with single-walled carbon nanotubes(SWCNTs)to form composites.The relationship between SWCNTs and polymer in different mass ratios was studied.The details are as follows:1.We designed and synthesized two polymers with different backbones structure,PIDT-EDOT and PIDTT-EDOT,to investigate the effects of the backbone structure on the thermoelectric properties.The study found that IDTT-based polymers with two thieno[3,2-b]thiophene(TT)unit exhibited.Good thermal stability and flatter planar structure after changing their backbone structure.After doping with Fe Cl3,The conductivity of polymer PIDTT-EDOT is significantly higher than that of polymer PIDT-EDOT,and its highest conductivity was 4.506 S cm-1,which is about 92 times than that of polymer PIDT-EDOT(0.054 S cm-1).These results indicate that increasing the conjugate length of the polymer is helpful to improve the thermoelectric performance of IDTT-based polymers.2.Based on IDTT unit,Selecting the IDTT unit which show better thermoelectric properties in the previous chapter,we designed and synthesized two polymers by using DFDTBT,DFBT,respectively,and explore the effect of different acceptor units on the thermoelectric properties.DFDTBT unit decrease the band gap of the polymer,which leads to a significant increase in conductivity and a decrease in Seebeck.3.After the introduction of 3T and DTT units,which have less electron-withdrawing features.It was found that the planarity of the polymer structures polymer PIDTT-3T has a great influence on the thermoelectric properties,at 412 K,the Seebeck coefficient of PIDTT-3T is 30.40 ?V K-1 with the highest power factor of 9.69 ?W m-1 K-2.The experimental results show that the introduction of thiophene units can improve the planarity of the polymer,and better planarity helps to increase the carrier mobility of the polymer,thereby improving the conductivity of the polymer;4.According to the previous two chapters,we prepared composite thermoelectric films with SWCNTs and IDTT-based polymer,it was found that strong ?-? interfacial interactions between IDTT-based polymer and SWCNTs were observed.And we systematically studied the effect of different mass ratio of SWCNTs on the thermoelectric properties.At room temperature,the electrical conductivity,Seebeck coefficient,and power factor of this composite material can reach 529.3 S cm-1,68.1 ?V K-1,and 80.9 ?W m-1 K-2,respectively.The composite exhibited the best thermoelectric performance,with a power factor of 183.9?W m-1 K-2 at 354 K when the mass ratio of IDTT-based polymer:SWCNT was 5:10.It was shows that the thermoelectric properties of IDTT-based polymer can be enhanced by combinding the IDTT-based polymer with carbon nanotubes. |
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