Efficient Pure Spin Current Propagation in Conjugated Polymer

Open-shell organic molecules have emerged as promising materials for spintronic devices due to their unpaired electrons and unique magnetic properties. Among these, donor-acceptor conjugated polymers (DA-CPs) have shown promise due to their diradical nature. However, their potential for spin transport has yet to be explored. Here, a specific DA-CP featuring cyclopentadithiophene (CPDT) as the donor unit and thidiazoloquinoxaline (TQ) as the acceptor unit was evaluated, to better determine the spin transport behavior of this system. Magnetic characterization of the polymer indicates that this material is paramagnetic and possesses a high-spin ground state. Ferromagnetic resonance (FMR) and inverse spin hall effect (ISHE) measurements were used to probe the propagation and conversion of pure spin currents. A pure spin current in the ferromagnetic layer (NiFe) was generated using FMR, injected into the polymer, and detected via ISHE in adjacent heavy metals (Pd or Cu). Efficient spin propagation was observed through micrometer-thick polymer films, indicating the spin diffusion length in the micrometer range, which is among the highest reported values for undoped organic molecules. These findings highlight the potential of donor-acceptor conjugated polymers as a platform for high-performance spintronic devices.