Efficient red electroluminescence from devices having multilayers of a europium complex

In order to get red electroluminescence from a europium (Eu) complex with h igh efficiency, a hole-injection layer was inserted between the Eu-complex layer and an indium-tin-oxide electrode, and a hole-blocking layer was inse rted between the Eu-complex and electron-transporting layers. To further im prove the efficiency, devices having multiple-stacked Eu-complex (2.5 nm)/h ole blocking (2.5 nm) units were fabricated. By stacking six units, the max imal luminance and emission efficiency of the red emission were increased t o more than twice that from a device with a single Eu-complex layer. (C) 20 00 American Institute of Physics. [S0003-6951(01)02801-7].