Manipulation of magneto-electroluminescence from exciplex-based spintronic organic light-emitting diodes

Abstract

Electron donor–acceptor-type thermally activated delay fluorescence (TADF) materials such as exciplexes possess abundant spin flip channels, which provide favorable potentials for novel multifunctional spintronic or spin-optoelectronic devices, and a feasible strategy for achieving high-performance organic light-emitting diodes (OLEDs) via reverse intersystem crossing (RISC) spin flip process. Although the spin flip process or magnetic effect in these materials and their non-magnetic OLEDs have been intensively studied, explorations on exciplex-based spintronic devices with ferromagnetic electrodes are rather rare. This is partially because of the significant performance deterioration induced by the ferromagnetic electrodes. In this work, spintronic-OLEDs are successfully fabricated by inserting ferromagnet nanolayers into non-magnetic OLEDs. By adjusting the spin-polarized cathodes, different magneto-electroluminescence (MEL) responses are realized. The MEL(B) responses are explained using a joint spin flip mechanism including hyperfine interaction (HFI), different g-factors between holes and electrons (Δg mechanism), and a difference in magnetic-field strength between two polarons (ΔB mechanism). Our results may provide some basic reference for the research and development of TADF-based spintronic and optoelectronic devices.