High-efficiency organic light-emitting diodes of phosphorescent PtAg2 heterotrinuclear acetylide complexes supported by triphosphine

Abstract

Three PtAg₂ heterotrinuclear complexes supported by dpmp [dpmp = bis(diphenylphosphinomethyl)phenylphosphine] were prepared using carbazole-functionalized acetylides with hole-transport character as co-ligands. As established by X-ray crystallography, the PtAg₂ array supported by dual dpmp exhibits a centre-symmetric linear arrangement with significant Pt–Ag interaction. They display intense phosphorescence in CH₂Cl₂ solutions (Φ_em = 56.9–65.3%) and doping films (Φ_em = 43.1–71.2%) at room temperature, originating primarily from ³[π(aromatic acetylides) → π*(dpmp)] ³LLCT and ³[π(aromatic acetylides) → s/p(PtAg₂)] ³LMCT triplet states mixed with some PtAg₂ cluster centred ³[d → s/p] character. Upon doping 8% PtAg₂ complexes with blended host materials consisting of hole-transport TCTA and electron-transport OXD-7 as light-emitting layers, high-efficiency solution-processed organic light-emitting diodes were achieved with 67.4 cd A⁻¹ peak current efficiency and 17.4% external quantum efficiency.