Lattice arrangement induced the transition from bipolar to <i>n</i>-type enhancing the spin polarization and the magnetic field dependent dipole effect in organic crystals

Abstract

The discovery of molecular entities is an effective way to expand and modulate the electronic and spin properties of organic semiconductors. In this work, we have fabricated organic cocrystals with identical donors and acceptors that undergo a unique structural rearrangement, leading to the formation of two polymorphs with distinct space groups. One is n-type, and the other one is bipolar. The variation in unipolar and bipolar structure significantly impacts the electric polarization, fluorescence lifetime, and spin polarization. By transitioning the transport from bipolar to n-type, a significant difference in charge–lattice interactions becomes evident, offering an enhancement in both spin polarization and electric dipolar polarization. Also, magnetic field could effectively tune electric dipolar polarization to present a magnetoelectric coupling in organic crystals. This facilitates the development of functional materials and devices in the field of organic magnetoelectrics.