High-efficiency yellow double-doped organic light-emitting devices based on phosphor-sensitized fluorescence

We demonstrate high-efficiency yellow organic light-emitting devices (OLEDs ) employing [2-methyl-6-[2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl) ethenyl]-4H-pyran-4-ylidene] propane-dinitrile (DCM2) as a fluorescent lumo phore, with a green electrophospho- rescent sensitizer, fac tris(2-phenylpy ridine) iridium [Ir(ppy)(3)] co-doped into a 4,4'-N,N(')dicarbazole-bipheny l host. The devices exhibit peak external fluorescent quantum and power eff iciencies of 9%+/-1% (25 cd/A) and 17 +/-2 lm/W at 0.01 mA/cm(2), respectiv ely. At 10 mA/cm(2), the efficiencies are 4.1%+/-0.5% (11 cd/A) and 3.1 +/- 0.3 lm/W. We show that this exceptionally high performance for a fluorescen t dye is due to the similar to 100% efficient transfer of both singlet and triplet excited states in the doubly doped host to the fluorescent material using Ir(ppy)(3) as a sensitizing agent. These results suggest that 100% i nternal quantum efficiency fluorescent OLEDs employing this sensitization p rocess are within reach. (C) 2001 American Institute of Physics.