Speakers

Prof. Yuguang Ma is a professor at South China University of Technology and an academician at the Chinese Academy of Sciences. Professor Ma is engaged in the basic scientific research of organic/polymer optoelectronic materials. (1) He first realized electroluminescence of phosphorescent materials and proposed the principle of improving the efficiency of organic light-emitting diode using phosphorescent materials, which made original contributions to the development of the second generation of luminescent (phosphorescent) materials. (2) He proposed the mechanism of "hot exciton" and the structural design principle of hybridized local and charge-transfer materials, making original contributions to the development of a new generation of cheap luminescent materials. (3) He invented the processing method of insoluble organic polymer functional material film with high efficiency electroluminescence and high conductivity, leading the new direction of polymer materials.

Room-temperature Ferromagnetism in Organic Semiconductor

Abstract

Ferromagnetic semiconductors are expected to solve the "post-Moore era" problems due to their dual characteristics as semiconductors and magnetic materials. The reported diluted magnetic semiconductors are ferromagnetic only at low temperature. "Can we make magnetic semiconductors at room temperature?" is one of 125 most challenging questions, published on Science 125th anniversary. Pure organic magnets were discovered in 1991 year and its Curie temperature was only at 0.65 K. Although room temperature organic magnets have been reported occasionally in recent years, their saturation magnetization is very low and they are electrically insulated. Here, we have achieved the world's first room-temperature organic ferromagnetic semiconductor by constructing strong intermolecular interactions of radical anion. By controlling the self-assembly process of reduced perylene diimide, we prepared radical anion aggregates, and the intermolecular π-π distance was close to 3.30 Å, which solved the problem of weak correlation of electron spins among radical anion and promoted the formation of long-range ferromagnetic ordering. The prepared materials have both room temperature ferromagnetic and semiconductor characteristics, with Curie temperature over 400 K, saturation magnetization up to 1.2 emu g^-1 and Hall mobility up to 0.5 cm² V^-1·s^-1, which brings hope for the application of organic ferromagnetic semiconductors. We show that constructing strong intermolecular interactions of radical anion is an effective way to realize organic ferromagnetic semiconductors.