High Triplet Energy Level Achieved by Tuning the Arrangement of Building Blocks in Phosphorescent Polymer Backbones for Furnishing High Electroluminescent Performances in Both Blue and White Organic Light-Emitting Devices

A high triplet energy level (E_T) of ca. 2.83 eV has been achieved in a novel polymer backbone through tuning the arrangement of two kinds of building blocks, showing enhanced hole injection/transporting capacity. Based on this new polymer backbone with high E_T, both blue and white phosphorescent polymers were successfully developed with a trade-off between high E_T and enhanced charge-carrier transporting ability. In addition, their photophysical features, electrochemical behaviors, and electroluminescent (EL) properties have been characterized in detail. Benefitting from the advantages associated with the novel polymer backbone, the blue phosphorescent polymers show top-ranking EL performances with a maximum luminance efficiency (η_L) of 15.22 cd A^-1, corresponding to a power efficiency ((η_P) of 12.64 lm W^-1, and external quantum efficiency ((η_ext) of 6.22% and the stable Commission Internationale de L'Eclairage (CIE) coordinates of (0.19, 0.38). Furthermore, blue-orange (B-O) complementary-colored white phosphorescent polymers based on this novel polymer backbone were also obtained showing encouraging EL efficiencies of 12.34 cd A^-1, 9.59 lm W^-1, and 4.10% in the optimized WOLED together with exceptionally stable CIE coordinates of (Δx = 0.014, Δy = 0.010) in a wide driving voltage range from 4 to 16 V. All of these attractive EL results achieved by these novel phosphorescent polymers show the great potential of this new polymer backbone in developing highly efficient phosphorescent polymers.