Using phosphorescent PtAu3 clusters for superior solution-processable organic light emitting diodes with very small efficiency roll-off

Abstract

A family of highly phosphorescent PtM₃ (M = Au, Ag) aromatic acetylide cluster complexes supported with tetraphosphine and stabilized by μ-chloride were synthesized by the use of weakly luminescent mononuclear Pt(PPh₃)₂(CCR)₂ (R = aryl) as precursors. The formation of PtM₃ cluster complexes involves the abstraction of chloride from dichloromethane. The dramatic difference between PtAg₃ and PtAu₃ cluster structures arises from the location of the Pt atom, which is at the center of the triangle-planar PtM₃ cluster for M = Ag whereas at one of the three corners in the PtM₃ triangle plane for M = Au. Perturbation of the chloride ion in complexation by using a halide-abstracting agent results in the formation of PtM₂ heterotrinuclear structures as demonstrated by X-ray crystallography. The PtAu₃ complexes display intense phosphorescence with quantum yields of over 90% in doped films. High-efficiency OLEDs based on PtAu₃ complexes were attained with an external quantum efficiency (EQE) over 18%. Most importantly, the optimized devices exhibit extremely small efficiency roll-off (less than 1%) at a practical brightness over 1000 cd m⁻², which is one of the best performances for solution-processable phosphorescent OLEDs.