Highly efficient red electrophosphorescent devices based on an iridium complex with trifluoromethyl-substituted pyrimidine ligand

Highly efficient red-emitting electrophosphorescent devices were fabricated by doping an iridium $\left(\mathrm{Ir}\right)$ complex containing trifluoromethyl ${(\mathrm{CF}}_3)$ -substituted pyrimidine ligand into a conjugated bipolar polyfluorene with triphenylamine and oxadiazole as side chains. The device efficiency can be enhanced through effective exciton confinement using a layer of 1,3,5-tris($N$ - phenylbenzimidazol-2-yl)benzene on the cathode side and a layer of in situ polymerized tetraphenyldiamine-perfluorocyclobutane on the anode side. For a blend with $5\mathrm{wt}\%$ of the $\mathrm{Ir}$ complex, a maximum external quantum efficiency of 7.9 photon/electron % and a maximum brightness of $15800\mathrm{cd}∕{\mathrm{m}}^2$ are reached with Commission Internationale de L’Eclairage chromaticity coordinates of $x=0.65$ and $y=0.34$ .