Magnetic field effects on the electroluminescence of organic light emitting devices: A tool to indicate the carrier mobility

Abstract

The magnetoelectroluminescence (MEL) of organic light emitting devices with a N,N′-bis(l-naphthyl)-N,N′-diphenyl-1,l′-biphentl-4,4′-diamine:tris-(8-hydroxyquinoline) aluminum (NPB:Alq3) mixed emission layer (EML) has been investigated. We find that MEL is maximized when the volume ratio of NPB of the mixed EML reaches 30% and the EML thickness is 40 nm. The features of MEL under various magnetic field strengths are insensitive to the change in EML thickness and mixing ratio. Meanwhile, MEL has a close relationship with the carrier mobility. We have conducted a theoretical study to further verify the relationship. Our experimental and theoretical results confirm that MEL can function as a tool to indicate the mobility.