trans-N-(Heterocyclic Carbene) Platinum(II) Acetylide Chromophores as Phosphors for OLED Applications

A family of complexes of the type trans-(NHC)(2)Pt(C C-Ar)(2) (NHC = N-heterocyclic carbene and Ar = substituted phenyl or 4-pyridyl) exhibits blue or blue-green phosphorescence. The photoluminescence is 10-50-fold more efficient when the materials are in dispersed in a solid poly(methyl methacrylate) glass compared to in THE solution. The phosphorescence quantum efficiencies in PMMA glass range from 0.20-0.65, varying with the structure of the aryl acetylide ligands. Organic light-emitting diodes (OLEDs) were fabricated by thermal evaporation, using bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO) as the host, and 15% of the trans-(NHC)(2)Pt(C C-Ar)(2) complexes as the dopant/emitters. Most of the OLEDs display good performance, with EL spectra that closely match the PL in the PMMA glass. The best performing materials have a peak EQE ranging from 9.6-14.1%, with deep blue spectral profiles (minimum CIE (0.16, 0.13)). Several of the complexes have deep HOMO poor EL performance attributed to inefficient host to emitter hole transfer.