基于噻唑单元D-A型共轭聚合物的设计合成及其热电性能研究

发布时间：2018-06-01 09:19

本文选题：热电材料 + 共轭聚合物　；参考：《深圳大学》2017年硕士论文

【摘要】：热电材料又称温差材料,由于热电材料可实现热能与电能直接转换,作为一种新型可持续发展的清洁能源材料而逐渐受到人们的关注。尽管无机热电材料经过了多年的发展,相关研究已经相对成熟,但是近年来,由于有机热电材料具有无毒、易制备、柔性、高的塞贝克系数及低热导率等优点,逐渐受到学者们的青睐。本文主要针对具有D-A结构的高分子热电材料展开研究,以强受体噻唑为基础单元,通过引入芴、噻吩及咔唑单元作为给体,系统探究噻唑类聚合物结构(烷基侧链和分子骨架)与热电性能之间的关系。选取其中具有高塞贝克系数的F8BT与单壁碳纳米管(SWCNT)进行复合,以期进一步提高复合材料的热电性能。通过对D-A型噻唑类聚合物热电性能的系统研究,我们发现可以通过调整烷基侧链长度、减小带隙、引入导电性好的给体及和导电性较好的SWCNT进行复合来提高热电性能。其具体内容如下:1.合成具有D-A结构的芴-噻唑类聚合物(F6BT,F8BT及F12BT),在不改变带隙前提下,探究烷基侧链对热电性能的影响。结果表明烷基侧链越短,分子堆积越明显,越有助于电子传输。因此F6BT拥有较好的热电性能,其电导率最高可达1.52 S/cm(22°C),功率因子为1.65μW m~(-1) K~(-2)。变温条件下,伴随温度的逐渐升高,分子间运动加剧,进而分子有序排列降低,分子间π-π堆积效应逐渐减弱,致使载流子迁移率减小,电导率下降,相反其赛贝克系数升高。2.在第1部分基础之上,选取容易制备且原料便宜的F8BT为引入噻吩单元,使聚合物带隙变窄,探究带隙变化对噻唑类聚合物热电性能影响。发现带隙变窄,电导率升高,塞贝克系数降低,但仍具有较高赛贝克系数,约为45μV/K。在不改变带隙的条件下,将给体换成导电性较好的咔唑单元,探究给体对热电性能的影响,发现咔唑单元的引入可以进一步提高材料的导电性,并且在90°C条件下,C8TBT的塞贝克系数可达335μV/K,功率因子可以达到13μW m~(-1) K~(-2)。3.在第2部分的基础之上,选取具有高塞贝克系数且容易制备的F8BT与导电性较好的SWCNT进行复合制备复合热电材料。发现加入SWCNT之后,复合材料电导率显著提高。伴随SWCNT质量分数的增加,电导率呈先增加后降低的趋势,然而SWCNT的含量对复合材料的塞贝克系数影响较小。当SWCNT质量分数为50%时,F8BT-Fe Cl3/SWCNT复合材料电导率可达1625 S/cm,功率因子为33.4μW m~(-1) K~(-2)。该研究表明,通过将F8BT与SWCNT复合,可以兼具SWCNT高的导电性与F8BT高的赛贝克系数,获得更优良的热电性能。
[Abstract]:Thermoelectric materials, also called thermoelectric materials, have been paid more and more attention as a new kind of clean energy materials for sustainable development, because thermoelectric materials can realize the direct conversion of thermal energy and electric energy. Although inorganic thermoelectric materials have been developed for many years, the related research has been relatively mature, but in recent years, due to the advantages of non-toxic, easy to prepare, flexible, high Seebeck coefficient and low thermal conductivity, organic thermoelectric materials have many advantages, such as non-toxic, easy preparation, high Seebeck coefficient and low thermal conductivity. Gradually attracted the favor of scholars. In this paper, the high molecular thermoelectric materials with D-A structure were studied. Based on the strong receptor thiazole, fluorene, thiophene and carbazole units were introduced as donors. The relationship between the structure of thiazole polymers (alkyl side chain and molecular skeleton) and thermoelectric properties was systematically investigated. In order to further improve the thermoelectric properties of the composites, F8BT with high Seebeck coefficient and SWCNT with single wall carbon nanotubes were selected. Through the systematic study of the thermoelectric properties of D-A thiazole polymers, we find that the thermoelectric properties can be improved by adjusting the length of alkyl side chain, reducing the band gap, introducing a donor with good conductivity and compounding with SWCNT with good conductivity. The details are as follows: 1. Fluorene thiazole polymers (F _ 6BTN, F _ 8BT and F _ 12BTN) with D-A structure were synthesized. The influence of alkyl side chain on thermoelectric properties was investigated without changing the band gap. The results show that the shorter the alkyl side chain, the more obvious the molecular stacking is, and the more favorable the electron transport is. Therefore, F6BT has good thermoelectric properties, its conductivity is up to 1.52 S/cm(22 掳C ~ (-1), and its power factor is 1.65 渭 W / m ~ (-1) K ~ (2 +). Under the condition of changing temperature, the intermolecular motion intensifies with the increase of temperature, and then the ordered arrangement of molecules decreases, and the 蟺-蟺 stacking effect weakens gradually, which results in the decrease of carrier mobility and the decrease of conductivity. On the contrary, the Seebeck coefficient increases by .2. On the basis of the first part, F8BT, which is easy to be prepared and cheap as raw material, is selected as the thiophene unit to narrow the band gap of the polymer. The influence of the band gap on the thermoelectric properties of thiazole polymers is investigated. It is found that the band gap becomes narrower, the conductivity increases, and the Seebeck coefficient decreases, but still has a higher Seebeck coefficient, which is about 45 渭 V / K / L. Under the condition that the band gap is not changed, the donor is replaced by carbazole unit with good electrical conductivity, and the effect of donor on thermoelectric property is explored. It is found that the introduction of carbazole unit can further improve the conductivity of the material. At 90 掳C, the Seebeck coefficient of C8TBT can reach 335 渭 V / K, and the power factor can reach 13 渭 W / m ~ (-1). On the basis of the second part, the composite thermoelectric materials were prepared by using F8BT with high Seebeck coefficient and SWCNT with good conductivity. It was found that the conductivity of the composites increased significantly after the addition of SWCNT. With the increase of mass fraction of SWCNT, the conductivity increased first and then decreased. However, the content of SWCNT had little effect on Seebeck coefficient of composites. When the mass fraction of SWCNT is 50, the conductivity of F8BT-Fe Cl3/SWCNT composites can reach 1625 S / cm, and the power factor is 33.4 渭 W / m ~ (-1) K ~ (2 +). The results show that by combining F8BT with SWCNT, the better thermoelectric properties can be obtained by combining the high conductivity of SWCNT with the high Seebeck coefficient of F8BT.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34

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