Magneto-Electroluminescence Study of Fringe Field in “Magnetic” Organic Light-Emitting Diodes

Abstract

Magneto-electroluminescence (MEL) represents the electroluminescence intensity change upon application of an external magnetic field. We show that the MEL field response in "magnetic" organic light-emitting diodes, where one electrode is ferromagnetic (FM), is a powerful technique for measuring the induced fringe field, B ⃗ F , from the FM electrode in the organic layer. We found that the in-plane fringe field, B ⃗ F∥ , from 3 nm Co and Ni 80 Fe 20 FM electrodes is proportional to the applied field, B ⃗ ∥ . The fringe field of the 3 nm Ni 80 Fe 20 film was also investigated for an applied out-ofplane magnetic field, B ⃗ ⊥ . We found that the out-of-plane fringe field has two components: a component that is parallel or antiparallel to B ⃗ ⊥ and remains unchanged with the distance, d, from the FM electrode and the other component that is highly inhomogeneous, parallel to the surface, and steeply decreases with d. We show that the obtained B ⃗ F is independent of the underlying mechanism for the MEL(B) response and thus may be considered universal.

Single-Molecule Magnetoluminescence from a Spatially Confined Persistent Diradical Emitter

“…Magnetic fields can modulate chemical reactions and materials’ properties in a noncontact and nondestructive manner; therefore, they play essential roles in various technologies and biological processes. − For example, magnetic field effects (MFEs) on electrical resistivity (magnetoresistance) have been applied to magnetic field sensors in computer memories and data storage devices . Magnetic fields are also used to modulate the photophysical and photochemical processes of materials. ,− Magnetic manipulation of exciton spin states is a particularly promising technology that enables enhanced efficiency of light emitting and energy devices, − control of photochemical reactions, high-resolution optical imaging, − and future quantum informatics . In this context, MFEs on molecular luminescence (i.e., magnetoluminescence, ML) have been intensively studied for luminescent closed-shell materials showing exciplex emission, − delayed fluorescence, phosphorescence, , triplet–triplet annihilation, − singlet fission, − electroluminescence, − and electrochemiluminescence. , In these systems, the ML occurs through the excitation-induced generation of spin-state-correlated species (e.g., radical pairs, polaron pairs, and triplet pairs) with several different spin multiplicities.…”

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

“…The VSM response can be well fitted with a modified error function. 34 The modified error function is defined as: The fit is shown in Fig. 7b, and the parameter fitting k = 0.02121 mT À1 .…”

“…Besides photo-physical investigations, the magnetic field effect (MFE) was also employed to study the spin flip mechanisms in nonmagnetic-and spin-OLEDs, where the EL intensity can be controlled by applying an external magnetic field. 27,34,35 In spin-OLEDs with ferromagnetic (FM) electrodes, another spin flip process caused by spatially inhomogeneous fringe field emanating from magnetic domains was founded. 34 The magnetic field gradients in FM electrodes lead to a locally varying spin-precession frequency, which can be explained by the DB mechanism.…”

“…27,34,35 In spin-OLEDs with ferromagnetic (FM) electrodes, another spin flip process caused by spatially inhomogeneous fringe field emanating from magnetic domains was founded. 34 The magnetic field gradients in FM electrodes lead to a locally varying spin-precession frequency, which can be explained by the DB mechanism. 30,36 Considering the abundant spin flip channels and excellent fluorescence properties of exciplex-type TADF, it will be particularly interesting to investigate the performance of their spin-LEDs with ferromagnetic electrodes.…”

Single-molecule Magnetoluminescence from a Spatially Confined Persistent Diradical Emitter

“…2 Magnetic fields are also used to modulate the photophysical and photochemical processes of materials. 1,[3][4][5] Magnetic manipulation of exciton spin states is a particularly promising technology that enables enhanced efficiency of light emitting and energy devices, [6][7][8][9][10] control of photochemical reactions, 11 high-resolution optical imaging, [12][13][14] and future quantum informatics 5 . In this context, MFEs on molecular luminescence (i.e., magnetoluminescence, ML) have been intensively studied for luminescent closed-shell materials showing exciplex emission, [15][16][17][18][19][20][21] delayed fluorescence, 22 phosphorescence, 23,24 triplettriplet annihilation, [25][26][27][28][29] singlet fission, [30][31][32][33] electroluminescence, [34][35][36][37] and electrochemiluminescence.…”