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 photo-crosslinking 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.