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IT Home reported on July 26 that the Institute of Chemistry of the Chinese Academy of Sciences issued a press release on July 24, announcing that Chinese scientists have made important progress in the research of high-performance organic thermoelectric materials, and the relevant research results were published online in the journal Nature.

Background of the project

In the 1970s, the scientific discovery of doped polyacetylene overturned the traditional perception that "plastic cannot conduct electricity", set off a research boom in optoelectronic molecular materials, gave birth to the organic light-emitting diode electronics industry, and spawned cutting-edge research directions such as organic photovoltaics and organic field-effect transistors, while also driving the start of the organic thermoelectric field.

Among them, the thermoelectric research of polymer systems can not only deepen or even change people's understanding of the thermoelectric conversion mechanism of soft matter systems, but also meet the urgent needs of the Internet of Things and wearable electronics for attached energy, which has great scientific significance.

However, compared with the existing thermoelectric material system,Polymer thermoelectric materials have long faced the bottleneck of low thermoelectric figure of merit (ZT), unable to meet the core indicator requirements of temperature difference power generation and solid-state refrigeration applications, directly restricting the rapid development of the field.

Project Description

The research team of Zhu Daoben/Di Chong'an from the Institute of Chemistry, Chinese Academy of Sciences, in collaboration with the research group of Zhang Deqing, the research group of Zhao Lidong from the Beijing University of Aeronautics and Astronautics, and six other research teams at home and abroad, proposed and constructed polymer multi-periodic heterojunction (PMHJ) thermoelectric materials.

This type of molecular assembly has a periodically ordered nanostructure, in which the thickness of both polymers is less than 10 nanometers, the adjacent interface is approximately 2 molecular layers and has bulk heterogeneous characteristics.

The research team used two polymers, PDPPSe-12 and PBTTT, combined with molecular cross-linking methods to construct PMHJ films with different structural characteristics, revealing the size effect of thermal conductivity and interface diffuse reflection effect.

Design concept of PMHJ structure and characterization results of time-of-flight secondary ion mass spectrometry

The study found that when the thickness of each polymer approached the mean free path of the "phonon" of the conjugated skeleton, the interface scattering was significantly enhanced and the lattice thermal conductivity of the film was reduced by more than 70% to 0.1 W m-1 K-1.

Solution-coated large-area PMHJ films and flexible power generation

Reconstructed interface of PMHJ films

In addition, the doped (6,4,4) PMHJ film exhibits excellent electrical transport properties, with a power factor of up to 628 μW m-1 K-2 and a thermoelectric figure of merit of 1.28 at 368 K, reaching the room temperature thermoelectric performance level of commercial materials, driving plastic-based thermoelectric materials into the ZT>1.0 era.

Project Significance

The above research breaks the cognitive limitation that existing high-performance polymer thermoelectric materials do not rely on heat transport regulation.It provides a new path for the continued development of the field of plastic-based thermoelectric materials.

IT Home attaches the reference address