Magnetic nanoparticles/PEDOT:PSS composite hole-injection layer for efficient organic light-emitting diodes

A multifunctional solution-processed composite hole-injection layer (HIL), based on the blends of magnetic nanoparticles (NPs) Fe3O4@G-poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), Fe3O4@SiO2-PEDOT:PSS and Fe3O4@Au-PEDOT:PSS, was used for application in high performance tris-(8-hydroxyquinoline) aluminum-based organic light emitting diodes (OLEDs). Compared to the control devices, a significant increase in the current efficiency of OLEDs with a composite HIL was realized, achieving maximum luminous efficiencies of 5.13 cd A(-1) (Fe3O4@G-PEDOT:PSS and Fe3O4@Au-PEDOT: PSS HIL), and of 4.83 cd A(-1) (Fe3O4@SiO2-PEDOT:PSS HIL), corresponding to a 35% and 38.2% increase in current efficiency, respectively. The increase in the performance of the OLEDs is attributed to the collective effects of light-scattering, localized surface plasmon resonance (LSPR) and the magnetic effect induced by the magnetic NPs in the HIL.