Unravelling the Molecular Origin of Organic Semiconductors with High‐Performance Thermoelectric Response

• Published in: Advanced functional materials 2021-02, Vol.31 (9), p.n/a
• Main Authors: Shi, Wen, Wong, Zicong Marvin, Deng, Tianqi, Wu, Gang, Yang, Shuo‐Wang
• Format: Article
• Language: English
• Subjects: Coupling (molecular); first‐principles calculations; Lattice vibration; material design; Materials science; Molecular structure; Organic semiconductors; Power factor; Principles; Q factors; Semiconductors; small‐molecule organic semiconductors; structure–property relationship; thermoelectric; Thermoelectric materials
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202007438

A decisive prerequisite toward systematic development of high‐efficiency organic thermoelectric materials is not only thoroughly understanding the microscopic physical processes controlling the performance, but also precisely correlating such processes and the macroscopic properties to the basic chemical structures. Here, by using multiscale first‐principles calculations, the interplay among thermoelectric properties, microscopic transport parameters, and molecular structures for the whole family of small‐molecule organic thermoelectric materials is rationalized, and general molecular design principles are concurrently formulated. It is unveiled that thermoelectric power factor of a wide variety of molecular semiconductors is directly proportional to a unified quality factor, and high‐performance thermoelectric response demands to boost the intermolecular electronic coupling, and to suppress the interaction of electron with lattice vibrations. Furthermore, it is uncovered that extending the π‐conjugated backbones along the long axis, and maximizing the networks of intermolecular S···S or CH···π contacts meet the proposed material design rule. A unified quality factor is proposed to quantify the thermoelectric power factor of small‐molecule organic thermoelectric materials based on first‐principles calculations. The high power factor requires the large intermolecular electronic coupling and the weak electron–vibration interaction. Extending the π‐conjugated backbones and maximizing the networks of intermolecular S···S or CH···π contacts are effective strategies for the enhanced power factor.