The effect of aromatic ring size in electron deficient semiconducting polymers for n-type organic thermoelectrics
The effect of aromatic ring size in electron deficient semiconducting polymers for n-type organic thermoelectrics
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DOI：
10.1039/d0tc03347b
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发表时间：
2020-11-21
影响因子：
6.4
通讯作者：
McCulloch, Iain
中科院分区：
文献类型：
--
作者：
Alsufyani, Maryam;Hallani, Rawad K.;McCulloch, Iain
N型半导体聚合物最近已被用于热电器件中，然而，与性能高得多的P型半导体相比，它们通常表现出低电导率和差的器件稳定性。这特别是由于n型半导体的低掺杂效率和差的电荷载流子迁移率。提高n型材料热电性能的策略包括优化掺杂剂的电子亲和势（EA）以改善掺杂过程，以及通过增强的分子堆积来提高电荷载流子迁移率。在这里，我们报告的设计，合成和表征的融合缺电子的n型共聚物纳入吸电子内酯单元沿着骨干。聚合物的合成使用无金属羟醛缩合条件下，探索扩大的中心苯环的萘环，对导电性的影响。当用N-DMBI掺杂时，从具有最大电子亲和势-4.68 eV的聚合物观察到高达0.28 S cm（-1）的电导率、-75 μ V K（-1）的Seebeck系数和0.16 μ W m（-1）K（-2）的最大功率因数。延长芳环降低了电子亲和力，由于降低了吸电子基团的密度，随后电导率降低了近两个数量级。
N-type semiconducting polymers have been recently utilized in thermoelectric devices, however they have typically exhibited low electrical conductivities and poor device stability, in contrast to p-type semiconductors, which have been much higher performing. This is due in particular to the n-type semiconductor's low doping efficiency, and poor charge carrier mobility. Strategies to enhance the thermoelectric performance of n-type materials include optimizing the electron affinity (EA) with respect to the dopant to improve the doping process and increasing the charge carrier mobility through enhanced molecular packing. Here, we report the design, synthesis and characterization of fused electron-deficient n-type copolymers incorporating the electron withdrawing lactone unit along the backbone. The polymers were synthesized using metal-free aldol condensation conditions to explore the effect of enlarging the central phenyl ring to a naphthalene ring, on the electrical conductivity. When n-doped with N-DMBI, electrical conductivities of up to 0.28 S cm(-1), Seebeck coefficients of -75 mu V K-1 and maximum Power factors of 0.16 mu W m(-1) K-2 were observed from the polymer with the largest electron affinity of -4.68 eV. Extending the aromatic ring reduced the electron affinity, due to reducing the density of electron withdrawing groups and subsequently the electrical conductivity reduced by almost two orders of magnitude.