Bright red light-emitting electroluminescence devices based on a functionalized europium complex

The complex tris(dibenzoylmethanato)(1-ethyl-2-(4'-carbazole-9-yl)phenyl imidazo[4,5-f]1,10-phenanthroline) europium (III), Eu(DBM)(3)(CPIP), was newly synthesized. Devices using this complex as emitter showed greatly enhanced performance benefiting from the improved hole-transporting properties of the complex and good stability. A double-layer device with the configuration of ITO/TPD(50 nm)/Eu(DBM)(3)(CPIP)(60nm)/Mg0.9Ag0.1(200 nm)/Ag(80 nm) exhibited Eu3+ based pure red emission with a brightness of 537 cd m(-2) at 13 V and the power efficiency of 0.089 lm W-1 at 6 V, 33 cd m(-2). A triple-layer device with the configuration of ITO/TPD(40 nm)/Eu(DBM)(3)(CPIP)(30 nm)/Eu(DBM)(3) Bath(50 nm)/Mg0.9Ag0.1 (200 nm)/Ag (80 nm) also emitted pure red light with a highest brightness of 1050 cd m(-2) at 16 V and the highest power efficiency of 0.50 lm W-1 at 8 V, 8 cd m(-2). The highest brightness 1460 cd m(-2) at 14 V was obtained from a four-layer device with the configuration of ITO/TPD(40 nm)/Eu(DBM)(3)(CPIP)(40 nm)/BCP(20 nm)/AlQ(10 nm)/Mg0.9Ag0.1( 200 nm)/Ag(80 nm) and the highest power efficiency of 0.54 lm W-1 at 7 V, 56 cd m(-2).