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

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.