Fan Xinyi, Deng Sihui, Cao Xu, Meng Bin, Hu Junli, Liu Jun
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China.
School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China.
ACS Appl Mater Interfaces. 2024 Sep 4;16(35):46741-46749. doi: 10.1021/acsami.4c08553. Epub 2024 Aug 20.
n-Type polythiophene represents a promising category of n-type polymer thermoelectric materials known for their straightforward structure and scalable synthesis. However, n-type polythiophene often suffers from a twisted backbone and poor stacking property when introducing high-density electron-withdrawing groups for a lower lowest unoccupied molecular orbital (LUMO) level, which is considered to be beneficial for n-doping efficiency. Herein, we developed two isomers of polythiophene derivatives, PTTz1 and PTTz2, by inserting thiazole units into the polythiophene backbone composed of thieno[3,4-]pyrrole-4,6-dione (TPD) and thiophene-3,4-dicarbonitrile (2CNT). Although PTTz1 and PTTz2 share a similar polymer skeleton, they differ in thiazole configuration, with the nitrogen atoms of the thiazole units oriented toward TPD and 2CNT, respectively. The insertion of thiazole units significantly planarizes the polythiophene backbone while largely preserving low LUMO levels. Notably, PTTz2 exhibits a more coplanar backbone and closer π-stacking compared to PTTz1, resulting in a greatly enhanced electron mobility. Both PTTz1 and PTTz2 can be easily n-doped due to their deep LUMO levels. PTTz2 demonstrates superior thermoelectric performance, with an electrical conductivity of 50.3 S cm and a power factor of 23.8 μW m K, which is approximately double that of PTTz1. This study highlights the impact of the thiazole unit on n-type polythiophene derivatives and provides valuable guidelines for the design of high-performance n-type polymer thermoelectric materials.
n型聚噻吩是一类很有前景的n型聚合物热电材料，以其结构简单和可扩展合成而闻名。然而，当引入高密度吸电子基团以获得更低的最低未占据分子轨道（LUMO）能级时，n型聚噻吩常常存在主链扭曲和堆积性能差的问题，而较低的LUMO能级被认为有利于n型掺杂效率。在此，我们通过将噻唑单元插入由噻吩并[3,4-b]吡咯-4,6-二酮（TPD）和噻吩-3,4-二甲腈（2CNT）组成的聚噻吩主链中，开发了两种聚噻吩衍生物异构体PTTz1和PTTz2。尽管PTTz1和PTTz2具有相似的聚合物骨架，但它们在噻唑构型上有所不同，噻唑单元的氮原子分别朝向TPD和2CNT。噻唑单元的插入显著地使聚噻吩主链平面化，同时很大程度上保持了低LUMO能级。值得注意的是，与PTTz1相比，PTTz2表现出更共面的主链和更紧密的π堆积，从而导致电子迁移率大大提高。由于其较深的LUMO能级，PTTz1和PTTz2都可以很容易地进行n型掺杂。PTTz2表现出优异的热电性能，电导率为50.3 S cm，功率因子为23.8 μW m-1 K-2，约为PTTz1的两倍。这项研究突出了噻唑单元对n型聚噻吩衍生物的影响，并为高性能n型聚合物热电材料的设计提供了有价值的指导。
