Solution-Processed Organic Light-Emitting Diodes Using a Photo-Crosslinkable Hole-Transporting Layer

Photo-crosslinkable hole transporting layer (HTL) consisting of a blend of poly(bis-4-butylphenyl-N,N-bisphenyl)benzidine (poly-TPD) and bis(4-azido-2,3,5,6-tetrafluorobenzoate) (FPA) was applied to red and green organic light-emitting diodes (OLEDs) by solution processing. This photocrosslinking reaction rendered the HTL insoluble in organic solvents and enabled subsequent solution deposition of an upper emissive layer. The solvent resistance of the photo-crosslinked poly-TPD:FPA (1 wt%) film was enhanced compared to that of the non-crosslinked neat poly-TPD film. Solution-processed red and green OLEDs with the poly-TPD:FPA (1 wt%) photo-crosslinked HTL exhibited higher device performances than those with the non-crosslinked poly-TPD HTL.