White Light Emission from Polymer Light-emitting Devices based on Blue and Red Phosphorescent Polymers

We demonstrate white light emission from polymer light-emitting devices (PLEDs) that are based on phosphorescent polymers consisting of a carbazole unit and a blue or red emitting Ir complex unit. The PLED using red phosphorescent polymer (RPP) or blue phosphorescent polymer (BPP) emitted blue (λ=476 nm) or red (λ=620 nm) light which is assigned to radiative relaxation from the triplet state of Ir complex units. High external quantum efficiencies of 6.5%, and 6.9% were obtained in the blue and red PLEDs, respectively. To make the white PLED, both BPP and RPP were used for the emissive layer, and the emission color was tuned by controlling the concentration ratio of both phosphorescent polymers. CIE coordinates of (0.34, 0.36) and external quantum efficiency of 6.0% were obtained at 100 cd/m2. This efficiency is the highest value in organic white-light-emitting devices.