Disorder‐Induced Dispersive Magneto‐Electroluminescence of Blue Emitters in Organic Light Emitting Diodes

Abstract

Disorder‐induced inhomogeneity in blue‐fluorescent‐based organic light‐emitting diodes (OLEDs) based on mixtures of host and guest molecules is studied using magneto‐electroluminescence, MEL(B), response based on the so called “Δg mechanism”, where Δg is the difference in the Landé g‐factor of electrons and holes. The disorder in the organic active layer is manifested by a unique non‐Lorentzian MEL(B) response that is analyzed using a distribution of spin lifetimes for the injected electron–hole pairs that is determined by a dispersive parameter, α (<1). The carriers’ inhomogeneous response also influences the free carrier absorption spectrum, which shows characteristic properties described by a dispersive parameter β (<1). From the measured MEL(B) response at various injection conditions it is found that α is robust at increasing current density showing that the inhomogeneity is governed by intrinsic disorder in the device active layer. Also the obtained increase in α at low temperature indicates that the organic layer becomes more ordered, where longer‐lived electron–hole spin pairs are formed.

Conversions from Normal to Abnormal Current‐Dependent ISC and from Abnormal to Normal Current‐Dependent RISC Processes in Exciplex‐Based OLEDs

“…[34,35] PP 1 and PP 3 can interconvert through ISC and RISC processes because they are almost degenerate in energy and the spin flipping can be realized under the hyperfine interaction (HFI). [3,[34][35][36][37] Although it is reported that the spin flipping between PP 1 and PP 3 also can be induced by Δg mechanism, [20,[38][39][40][41] Δg mechanism could be ruled out in this work. The related discussion is shown in Text S1, Supporting Information.…”

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

“…S1, ESI †). 43 After inserting the FM Co and Ni nanolayers, the room temperature MEL decreases to B18.8% and the FWHM increases to 48.9 mT. The decrease in MEL may be related to the reduced electron injection ability caused by the Ni cathode.…”

Study on the exciton dynamic processes of exciplex host-guest system by transient magnetic field effects

“…Steady MFE measurements were further performed on devices to reveal the important role of DET from exciplex host to DCJTB guest. External magnetic field can slightly alter the formation ratio of singlet to triplet in exciplex host, causing an MFE on EL intensity [25][26][27][28][29][30][31][32]. In an energy transfer host-guest system, the DCJTB emission will certainly inherit the host MFE profiles.…”