Anisotropic Organic Magnetoresistance in Fused-Ring Electron-Acceptor-Based Bulk Heterojunction Systems

Anisotropic organic magnetoresistance (AOMR) is unlikely and challenging to detect in organic semiconductors, because of their energetic disorder character and random molecular arrangements in solid films. Nevertheless, some fused-ring electron acceptor (FREA)-based organic bulk heterojunctions (BHJs) exhibit decent molecular growth modes, which may be of merit for the generation of remarkable AOMR and heretofore uninvestigated. In this work, we experimentally demonstrate the out-of-plane and in-plane AOMR with 2-fold symmetry in the ambient condition for prototypical organic blends such as PM6:Y6 and PM6:IT-4F. The phenomena cannot be equally observed in a conventional fullerene-based organic BHJ. Based on our microscopically theoretical models for the analyses of the effect, we postulate that AOMR originate from an interplay of the anisotropic Δ g factor and hyperfine field (HF) induced spin mixing mechanism. We believe that a complete understanding of AOMR in the organic BHJ system opens a new avenue for the development of magnetic navigations and sensors.