The latest research progress of polymer thermoelectric materials by Peijian wangjieyu group, School of chemistry and molecular engineering, Peking University

Thermoelectric device is a kind of semiconductor device which uses the thermoelectric effect of semiconductor to realize the direct conversion between thermal energy and electric energy It has an important application in the field of thermal power generation under extreme conditions, local temperature regulation in micro area and so on Organic polymer thermoelectric materials have great application value in the next generation of thermoelectric devices due to their low thermal conductivity, solvability, and light and thin flexibility However, the research progress of n-type polymer thermoelectric materials, which is the indispensable part of polymer thermoelectric devices, is relatively slow, and their thermoelectric performance is generally lower than that of p-type thermoelectric materials How to improve the thermoelectric properties by improving the molecular structure of N type polymer is the key to the research in the field of polymer thermoelectric materials Peijian Wang Jieyu research group of School of chemistry and molecular engineering of Peking University, in cooperation with Zhu Daoben and di Chongan, Institute of chemistry, Chinese Academy of Sciences, designed and developed N-donor fragments modified with fluorine atoms The electron mobility of polymer is maintained by the interaction of donor and acceptor between polymer chains, and the electron affinity of polymer is increased by introducing fluorine atoms to improve the efficiency of N-doping The synergistic effect of the two greatly improves the n-type conductivity of polymer By further improving the Seebeck coefficient of the polymer, the team successfully improved the thermoelectric performance of the n-type to receptor polymer by three orders of magnitude The conductivity and power factor of the n-type polymer with fluorine atom increased to 1.3 s / cm and 4.6 μ w / Mk 2, which is the best performance of the n-type polymer thermoelectric materials Through the characterization of EPR, UV and X-ray photoelectron spectroscopy, it is proved that the introduction of fluorine atom improves the N-doping ability of the polymer The results of FET devices show that the introduction of fluorine improves the electron mobility of the polymer in n-doped state The conductivity of the polymer is 1000 times higher than that of the polymer without fluorine atom In addition, grazing incidence X-ray diffraction, atomic force microscopy and conducting atomic force microscopy experiments show that the introduction of fluorine atoms changes the molecular arrangement of the polymer, improves the miscibility of the polymer and the dopant, and changes the polymer from the state of "local doping" to the state of "uniform doping", thus maintaining the high n-type Seebeck coefficient of the doped polymer To sum up, these latest research progress shows that compared with the properties in the intrinsic state, the electrical properties and micro nano structure of the polymer in the doping state have more important influence on its thermoelectric properties On the other hand, on the premise of effectively improving the efficiency of N-doping, the fluorine atom modification on the donor segment can improve the electronic mobility of the doped polymer and the miscibility between the polymer and the dopant, thus greatly improving the n-type thermoelectric properties of the polymer This "donor modification" design strategy is relatively simple, which can be extended to a large number of other n-type donor receptor polymer thermoelectric properties research, and is expected to greatly expand the n-type thermoelectric polymer family This research work was published in advanced materials, a top journal in the field of materials and Engineering Science (DOI: 10.1002 / ADMA 201802850) The first author of this paper is Yang Chiyuan, a doctoral student in the school of chemistry and molecular engineering, Peking University.