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The phosphorescence polymer LEDs (PhPLEDs) with the structure of ITO/PEDOT:PSS/PVK:Ir(ppy) 3 : PFO:Ir(pq) 2 acac/TPBI/LiF/Al were fabricated to investigate the effect of doping concentrations on the electrical and optical properties of PhPLEDs. The PVK(poly-vinylcarbazole) and Ir(ppy) 3 [tris(2-phenylpyridine)iridium(III)] polymers were used as the host and guest materials. The PFO[poly(9,9-dioctylfluorene)] and Ir(pq) 2 (acac) [bis(2-phenyl-1-quinoline)iridiumacety lacetonate] were also introduced as other guest materials for the white emission. The Ir(pq) 2 acac concentrations was changed ranging from 1.0 to 5.0 volume % (vol %) in the emission layer. The concentration of PVK:Ir(ppy) 3 :PFO was fixed with 100:2.0:1.0 in vol %, respectively. The white PhPLEDs were obtained for the samples with 5.0 vol % of Ir(pq) 2 acac material and the maximum luminance was found to be 2430 cd/m 2 . The CIE color coordinators were ranged with x, y = 0.32~0.33, 0.33~0.34 at 8V, showing good white color.

Flexible phosphorescence polymer light emitting diodes (PhPLEDs) with PEN/ITO/PEDOT:PSS/ PVK:Ir(ppy)3/TPBI/LiF/Al structure were fabricated to investigate the effects of Ir(ppy)3 doping concentrations on the optical and electrical properties of the devices. PVK and Ir(ppy)3 conjugated polymers as host and guest materials in the emission layer were spun coated at various concentrations of Ir(ppy)3 ranging from 2.0 to 8.0 vol%. As the concentration of Ir(ppy)3 increased from 2.0 to 6.0 vol%, the electrical and optical properties of the flexible PhPLEDs were improved clearly. Maximum luminance and current density were obtained for a PhPLED with an Ir(ppy)3 concentration of 6.0 vol%, with 6815 cd/m2 and 393 mA/cm2 at 9 V. The current efficiency tends to increase with the Ir(ppy)3 concentration, because of the formation of the excitons required to emit light.