Manipulation of Emission Colors Based on Intrinsic and Extrinsic Magneto-Electroluminescence from Exciplex Organic Light-Emitting Diodes

Abstract: Exciplex organic light-emitting diodes (XOLEDs) utilize nonemissive triplet excitons via a reverse intersystem crossing process of thermally activated delayed fluorescence. The small energy difference between the lowest singlet and triplet levels of exciplex also allows a magnetic field to manipulate their populations, thereby achieving ultralarge “intrinsic” magneto-electroluminescence (MEL) in XOLEDs. Here we incorporate it into a hybrid type of spintronic device (“hybrid spin-XOLED”), where the XOLED is connected to a magnetic tunnel junction with large magnetoresistance, to introduce an “extrinsic” MEL response that interferes with the “intrinsic” MEL. The ratio between two MEL contributions, the MEL value, and the field response were altered by changing the exciplex layer thickness or actively manipulated by adding another current source that drives the XOLED. Most importantly, by involving two XOLEDs (green and red) in the same circuit, the hybrid spin-XOLED shows a color change when sweeping the magnetic field, which provides an alternative way for future OLED display technologies.