基于二噻吩并吡咯的D-A共轭聚合物的合成及热电性能研究

doi:10.12422/j.issn.1006-396X.2024.03.001

摘要/Abstract

摘要：

为探究D-A共轭聚合物中给体单元长度对其热电性能的影响，设计合成了3种含不同给体单元长度的二噻吩并吡咯（DTP）类的D-A共轭聚合物（PDPP-DTP、PDPP-2DTP、PDPP-3DTP），通过电化学表征结合密度泛函理论计算的方法研究了给体单元长度对聚合物能级的影响，并以三氯化铁作为掺杂剂对聚合物薄膜进行氧化掺杂，研究了其光学性质、热电性能及电阻随温度变化的规律。结果表明，随着DTP类给体单元长度的延长，聚合物的HOMO能级逐渐升高，使其更容易氧化掺杂；在相同的掺杂剂浓度下，掺杂后聚合物的电导率随着给体单元长度的延长而升高；PDPP-3DTP的最高电导率达到302.3 S/cm，远高于PDPP-2DTP（106.2 S/cm）和PDPP-DTP（64.7 S/cm）；随着给体单元长度的延长，聚合物薄膜的电荷传输能垒逐渐降低，有利于提高掺杂薄膜的电导率；随着给体单元长度的延长，掺杂后聚合物薄膜的塞贝克系数降低；聚合物PDPP-2DTP经掺杂优化后，其热电功率因子最高，其值达到19.4 μW/(m?K²)。

关键词: D-A共轭聚合物, 热电, 二噻吩并吡咯, 给体单元长度, 掺杂

Abstract:

To investigate the effect of donor unit length on the thermoelectric properties of D-A conjugated polymer,three D-A conjugated polymers(PDPP-DTP,PDPP-2DTP,PDPP-3DTP) based on dithieno[3,2-b:2′,3′-d]pyrrole (DTP) with different donor unit lengths were designed and synthesized.The influence of donor unit lengths on the energy levels of the polymers was studied by electrochemical characterization and density functional theory calculations.With ferric chloride as dopant,the polymer films were oxidation doped.Their optical and thermoelectric properties as well as the temperature dependent resistance were discussed.The results show that the HOMO energy levels of the polymers gradually increase with the extension of the length of the DTP-like donor unit,which makes them easier to be oxidatively doped.At the same dopant concentration,the doped polymers exhibit higher conductivity with the extension of the donor unit length.Among them,PDPP-3DTP shows the highest electrical conductivity of 302.3 S/cm,which is much higher than that of PDPP-2DTP(106.2 S/cm) and PDPP-DTP(64.7 S/cm).The charge transport energy barrier of the polymer films gradually decreases with the extension of the length of the donor unit,which is beneficial for the enhancement of electrical conductivity of doped films.However,the Seebeck coefficient of the doped polymer film decreases with the extension of the length of the donor unit,and the final polymer PDPP-2DTP is doped and optimized to have the highest thermoelectric power factor of 19.4 μW/(m·K²).

Key words: D-A conjugated polymers, Thermoelectric, Dithieno[3,2-b:2′,3′-d]pyrrole, Donor unit length, Doping

中图分类号:

TQ317.5

林婷, 张宇航, 李慧, 李鹏程. 基于二噻吩并吡咯的D-A共轭聚合物的合成及热电性能研究[J]. 石油化工高等学校学报, 2024, 37(3): 1-10.

Ting LIN, Yuhang ZHANG, Hui LI, Pengcheng LI. Synthesis and Thermoelectric Properties of Dithieno[3,2-b:2′,3′-d]pyrrole-Based D-A Conjugated Polymers[J]. Journal of Petrochemical Universities, 2024, 37(3): 1-10.

图/表 8

图1 单体和聚合物的分子结构及合成路线

Fig.1 Molecular structure and synthesis route of intermediates and polymers

表1 聚合物的 Mn 和PDI

Table 1 Molecular weight and PDI of the polymers

聚合物	M_n/kDa	PDI
PDPP-DTP	13.9	3.0
PDPP-2DTP	20.2	1.4
PDPP-3DTP	7.2	1.5

图2 聚合物的循环伏安图

Fig.2 Cyclic voltammograms of the polymers

表2 聚合物的电化学性质参数

Table 2 Electrochemical properties parameters of the polymers

聚合物	$E H O M O c v$ /eV	$E L U M O c v$ /eV	E $g c v$ /eV
PDPP-DTP	-4.84	-3.34	1.53
PDPP-2DTP	-4.75	-3.32	1.23
PDPP-3DTP	-4.47	-3.31	1.13

表2 聚合物的电化学性质参数

Table 2 Electrochemical properties parameters of the polymers

聚合物	$E H O M O c v$ /eV	$E L U M O c v$ /eV	E $g c v$ /eV
PDPP-DTP	-4.84	-3.34	1.53
PDPP-2DTP	-4.75	-3.32	1.23
PDPP-3DTP	-4.47	-3.31	1.13

图3 PDPP-DTP、PDPP-2DTP、PDPP-3DTP的DFT模拟计算结果注：D1-D7为相邻芳香环平面之间的二面角。

Fig.3 DFT simulation calculation results of PDPP-DTP，PDPP-2DTP and PDPP-3DTP

图4 PDPP-DTP、PDPP-2DTP、PDPP-3DTP在不同掺杂剂浓度下的紫外可见近红外吸收光谱和Ipolaron/Ineutral

Fig.4 Ultraviolet-visible-near-infrared absorption spectra and Ipolaron /Ineutral of PDPP-DTP and PDPP-2DTP，PDPP-3DTP at different doping concentrations

图5 聚合物在不同掺杂剂浓度下的电导率、塞贝克系数及功率因子

Fig.5 Conductivity，seebeck coefficient and PF of the polymer at different doping concentrations

图6 最佳掺杂条件下聚合物薄膜的温度与电阻的关系曲线

Fig.6 Temperature dependence curve of polymer film under optimal doping conditions

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