High-efficiency organic light-emitting diodes of phosphorescent PtAg2 heterotrinuclear acetylide complexes supported by triphosphine
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 (Φem = 56.9–65.3%) and doping films (Φem = 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.