Efficient white light-emission in organic multilayer electroluminescence devices

摘要

We report efficient white light-emitting devices with multiple emission layers. The devices consist of a blue-emitting 4,4'bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (a-NPD), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) doped with red fluorescent dye of 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j]quinolizin-8-yl) vinyl]-4H-pyran) (DCM2), BCP with variable thickness, and a green-emitting tris(8-hydroxyquinoline) aluminum (Alq_3). The thickness of the BCP layer and the concentration of DCM2 are tuned to achieve a balanced white emission. The device with the structure of ITO/a-NPD (50 nm)/BCP:DCM2 (1 %, 3 nm)/BCP (2 nm)/Alq_3 (50 nm)/LiF (0.5 nm)/AI shows a white emission with a maximum luminance of 22,570 cd/m~2 at 13.5 V. At a luminance of 100 cd/m~2 under the current density of 1.5 mA/cm~2 and the bias voltage of 5.6 V, the power efficiency is 3 Im/W and the external quantum efficiency is 2.5 %.