Enhanced Red Emission from Fluorescent Organic Light-Emitting Devices Utilizing a Phosphorescent Sensitizer

Abstract

Highly efficient red organic light-emtting devices that employ 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as a fluorescent dye, with a green phosphorescent-sensitizer, fac tris(2-phenylpridine) iridium (Ir(ppy)3) doped in a 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBi) host are demonstrated. The OLEDs at the concentration of 10:2 with red emission have the maximum brightness and luminance efficiency of 10000 cd/m2 (at 19 V) and 3.6 cd/A (at 5 V), respectively, which is higher than most of the fluorescent red organic light-emitting diodes (OLEDs). We attribute the improvement of the double-doped devices to the efficient energy transfer of both singlet and triplet excited states in the double-doped host to the fluorescent material using Ir(ppy)3 as a sensitizing agent.