The utilization of molecular phosphorescent dyes in polymer-based organic light emitting diodes (OLEDs) was investigated by codoping several phosphorescent dopants into poly(N-vinylcarbazole) (PVK)-based single layer light emitting diodes (LEDs). In particular, green fac-tris(2-phenylpyridine)iridium(III), [Ir(ppy)3], red tris(4,7-diphenyl-1,10-phenanthroline)rhenium dications, [Ru(4,7-Ph2-phen)3]2+, and (2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin)platinum(II) (PtOEP) were used. In the phosphorescence dye doubly doped PVK system ca. x wt % [Ru(4,7-Ph2-phen)3]2+:1wt % Ir(ppy)3:PVK(x) 0.5-5), the intensity ratio (Ri) of red emission vs green emission as a function of doping ratio (Rc) of [Ru(4,7-Ph2-phen)3]2+ vs Ir(ppy)3 is found according to a power-law function with the exponent of 2.0 (0.2 for photoluminescence, which obey the power law with Ri

We demonstrate novel organic light-emitting diode (LED) materials that contain a green phosphorescent dye (dmbpy)Re(CO)3Cl (dmbpy 4,4'-dimethyl-2,2'-bipyridine), and a red fluorescent dye 4-dicyanomethylene-6-(p-dimethylaminostyryl)-2-methyl-4H-pyran (DCM) as dopants and polyvinylcarbazole (PVK) as the host. The photoluminescence (PL) and electroluminescence (EL) properties of these complex materials were studied. The energy transfer efficiency from PVK host to DCM is increased by the (dmbpy)Re(CO)3Cl co-dopant, which has an emission energy between that of PVK and DCM. The (dmbpy)Re(CO)3Cl, which emits a long-lived phosphorescence, is used as an energy coupler, providing the possibility to harvest both singlet and triplet energy in the devices. The pure red emission from DCM was observed from PL and EL spectra of (dmbpy)Re(CO)3-CI(>2.0 wt.-% ):DCM(>0.5 wt.%) doped PVK films, demonstrating an efficient energy transfer from PVK and (dmbpy)Re(CO)3-CI to DCM. By optimizing the concentration of DCM and (dmbpy)Re(CO)3Cl in PVK, a maximum EL quantum efficiency of 0.42 cd A 1 at a current density of 9.5 mA cm 2 was obtained. The EL quantum efficiency of the doubly doped device is significantly enhanced in comparison with both a DCM-only doped PVK device and a DCM-doped PVK device with the green fluorescent dye Alq3 as co-dopant. The improvement in the operating characteristics of the phosphorescent and fluorescent dye doubly doped device is attributed to efficient energy transler in the system, in which both triplet and singlet excitons are used for resultant emission in the polymer device.

The electroluminescence [EL] from a dinuclear-gold(I)-chlorate compound containing bridging phosphine ligands [Au2]dppm(Cl2) as emitting layer is reported. Devices with a structure Al/Au2(dppm)Cl2 /indium-tin-oxide demonstrated a uniform emission under the driving voltage below 1 V. The EL emission was from triplet excited state and the emission color of the device was found to depend on the deposition rate of Au2(dppm)Cl2, which can be explained as the different aggregation forms of the stacking compound in the deposition process.