Highly Phosphorescent Dimers of PtAu₂ Complexes and the Use in Solution-Processed OLEDs

Two asymmetric PtAu₂ complexes having HC≡CC₆H₄C≡CH (1,4-diethynylbenzene) or HC≡CCarbC≡CH (2,7-diethynyl-9-(2,3,5,6-tetrafluorophenyl)-9H-carbazole) and the corresponding bis(acetylide)-linked Pt₂Au₄ complexes are prepared and characterized. The structures of PtAu₂ complexes 1 and 3 together with Pt₂Au₄ complex 2 are determined by X-ray crystallography. Relative to PtAu₂ complexes, bis(acetylide)-linked Pt₂Au₄ complexes not only display a distinct red shift of the emission but also provide a much higher phosphorescent efficiency. Utilizing highly emissive Pt₂Au₄ complexes as phosphorescent dopants, high-efficiency solution-processed OLEDs are obtained with peak current efficiency of 75.9 cd A^-1 and external quantum efficiency of 19.0% at luminance of 336 cd m^-2 and voltage of 5.2 V. When two PtAu₂ moieties are linked by a bis(acetylide) ligand, the corresponding Pt₂Au₄ complexes show a much improved electroluminescent performance compared with that of asymmetric PtAu₂ complexes.