Carbazole-functionalized europium complex and its high-efficiency organic electroluminescent properties

Abstract

A complex tris(dibenzoylmethanato){1-ethyl-2-$\mathrm{(N}$ -ethyl-carbazole-yl-4) imidazo[4,5-f]1,10phenanthroline} europium(III) $[\mathrm{Eu}(\mathrm{DBM}{)}_3\mathrm{phencarz}]$ functionalized by a hole-transport group carbazole was synthesized. Devices using this complex as emitter showed greatly enhanced performance benefited from the increased hole-transport properties and efficient energy transfer from carbazole to the central ions. A 58-nm-single-layer device gave a brightness of $\text{20\hspace{0.17em}}{\mathrm{cd/m}}^2$ at 15 V. The highest power efficiency of 2.7 lm/W at 5 V and $\text{0.5\hspace{0.17em}}{\mathrm{cd/m}}^2$ and the luminance exceeding $2000$ ${\mathrm{cd/m}}^2$ at 20 V was obtained from a device with the configuration of $\mathrm{ITO/TPD}\text{(20}$ $\mathrm{nm}\mathrm{)/}\mathrm{Eu}(\mathrm{DBM}{)}_3\mathrm{phencarz}\text{(40}$ $\mathrm{nm}\mathrm{)/}\mathrm{BCP}\text{(20}$ $\mathrm{nm}\mathrm{)/}\mathrm{AlQ}\text{(40}$ $\mathrm{nm}\mathrm{)/}{\mathrm{Mg}}_{\text{0.9}}{\mathrm{Ag}}_{\text{0.1}}\text{(200}$ $\mathrm{nm}\mathrm{)/}\mathrm{Ag}\text{(80}$ nm).