Dinuclear Pt-II Complexes with Strong Blue Phosphorescence for Operationally Stable Organic Light-Emitting Diodes with EQE up to 23 % at 1000 cd m(-2)

Here we describe the synthesis and characterization of a new class of dinuclear Pt-II complexes with blue phosphorescence. Bulky N-heterocyclic carbene and tethered bridging ligands were employed to suppress photo-induced structural changes and to improve thermal stability of the complexes. These complexes show mixed (IL)-I-3/(MLCT)-M-3 blue emission (approximate to 460 nm) with emission quantum yields of up to 0.95, emission lifetimes of as low as 1.3 mu s and radiative decay rate constants of up to 7.3x10(5) s(-1) in 4 wt % doped PMMA films; the latter is attributed to a (MLCT)-M-1 excited state having high metal character (resulting in a large SOC) and a large transition dipole moment, based on DFT calculations. Phosphor-sensitized blue hyper-OLEDs with Commission Internationale de L'Eclairage (CIE) coordinates of (0.13, 0.12) showed a maximum EQE of 23.4 % with a full-width-at-half-maximum of 18 nm and a LT50 >250 h at an L-0 of 1000 cd m(-2).