An n‐Type Polythiophene Derivative with Excellent Thermoelectric Performance

Abstract

Typical n‐type conjugated polymers are based on fused‐ring electron‐accepting building blocks. Herein, we report a non‐fused‐ring strategy to design n‐type conjugated polymers, i.e. introducing electron‐withdrawing imide or cyano groups to each thiophene unit of a non‐fused‐ring polythiophene backbone. The resulting polymer, n‐PT1, shows low LUMO/HOMO energy levels of −3.91 eV/−6.22 eV, high electron mobility of 0.39 cm2 V−1 s−1 and high crystallinity in thin film. After n‐doping, n‐PT1 exhibits excellent thermoelectric performance with an electrical conductivity of 61.2 S cm−1 and a power factor (PF) of 141.7 μW m−1 K−2. This PF is the highest value reported so far for n‐type conjugated polymers and this is the first time for polythiophene derivatives to be used in n‐type organic thermoelectrics. The excellent thermoelectric performance of n‐PT1 is due to its superior tolerance to doping. This work indicates that polythiophene derivatives without fused rings are low‐cost and high‐performance n‐type conjugated polymers.

A Highly Conductive n-Type Polythiophene Derivative: Effect of Molecular Weight on n-Doping Behavior and Thermoelectric Performance

“…The two monomers, namely, ditrimethyltin monomer (M1) and dibromo monomer (M2), were meticulously synthesized using the previously reported methods. 14 1 and Figure S1). The chemical structure of the three polythiophene derivatives has been confirmed through the use of 1 H NMR spectroscopy (Supporting Information).…”

“…The simplicity of n-PT2’s chemical structure allows for facile and well-established reactions to yield the desired product. The two monomers, namely, ditrimethyltin monomer (M1) and dibromo monomer (M2), were meticulously synthesized using the previously reported methods . The meticulous Stille polycondensation of M1 and M2 yielded n-PT2–8 kDa, n-PT2–22 kDa, and n-PT2–36 kDa (Scheme S1, Supporting Information).…”

“…In the early stage, an n-type polythiophene was developed, which has low LUMO energy levels (E LUMO ) and high electron mobility, representing a class of high-performance n-type polymers with a nonfused-ring structure. 14 Herein, we further study the n-type molecular doping and corresponding thermoelectric properties of this kind of conjugated polymer with various molecular weights. This work further proves the potential of n-type polythiophene derivatives as highconductivity materials and highlights a useful strategy for improving n-doping and thermoelectric performance by regulating molecular weight.…”

“…Low-cost, solution-processable high-conductivity polymers represent a pivotal technology that facilitates the development of various optoelectronic and bioelectronic applications. , They serve widely as electron/hole transport layers in organic solar cells (OSCs) and organic light-emitting diodes (OLEDs), , as well as the active material in electrochromic devices (OECs), organic electrochemical transistors (OECTs), , chemical/biological sensors, electric double-layer capacitors (EDLCs), stretchable electronic devices, organic thermoelectric generators (OTEs), − and organic-based neuroinspired computational platforms . Chemical doping presents itself as an efficient means to enhance the electrical conductivity (σ) of conjugated polymers. − At present, the electrical conductivities of many p-doped polymers have exceeded 1000 S cm –1 ; however, n-doping of conjugated polymers is more challenging and rarely gives a conductivity of >100 S cm –1 . ,, In OTEs and other fields, both p-doped polymers and n-doped polymers with high conductivities are required . At present, the number and types of n-doped conductive polymers are far less than p-doped conductive polymers, so it is urgent to develop novel high-performance n-doped conductive polymers to improve n-type conductivity. , …”

Organic Thermoelectric Materials from n‐Type Polymer Semiconductors

“…Recently, Liu et al synthesized a novel TPD-based n-type polymer by the introduction of electronwithdrawing imide and cyano on polythiophene backbone (Figure 4a). [25] The result polymer n-PT1 exhibited low LUMO/ HOMO of À 3.91 eV/-6.22 eV and high electron mobility of 0.39 cm 2 V À 1 s À 1 . They studied the optimized conformation of n-PT1, the non-covalent S•••O and hydrogen bond resulting in the fully coplanar conformation.…”