Strategic molecular engineering of blue phosphorescent Pt(II)compounds for the development of high-efficiency single-doped white OLEDs

초록

We synthesized two novel Pt(II) beta-diketonate compounds, 2 ',6 '-dimethoxy-4-tert-butyl-2,3 '-bipyridinato-N,C-4 ')platinum(II)(acetylactonate-O,O) (1) and 2 ',6 '-dimethoxy-4-trimethylsilyl-2,3 '-bipyridinato-N,C-4 ')platinum(II)(acetylactonate-O,O) (2), to develop blue phosphorescent compounds and systematically investigated their photoluminescent and electroluminescent characteristics. The compounds 1 and 2 exhibited bright sky-blue phosphorescence, with a phosphorescence maximum (lambda(max)) at 465 nm and 475 nm, respectively. The luminescence quantum yields were found to be 0.63 for 1 and 0.93 for 2. At high concentrations, both compounds exhibited bright red emission originating from the formation of excimer. However, compound 2, due to effective intermolecular interactions, exhibited a more red-shifted emission than compound 1 at the same concentration.For fabricating phosphorescent organic light-emitting diodes, the compounds 1 and 2 were used as dopants, and a 50:50 mixture of 3 '-di(9H-carbazol-9-yl)-1,1 '-biphenyl:9-(3 '-carbazol-9-yl-5-cyano-biphenyl-3-yl)-9H-carbazole-3-carbonitrile was used as the mixed host. When doped with 20 wt% of compound 2, the electroluminescent device exhibited the best performance, achieving an external quantum efficiency (EQE) of 13.7% at 100 cd/m(2) and current efficiency of 35.5 cd A(-1). Remarkably, the single-doped compound 2-based device achieved emission with Commission Internationale de L'Eclairage coordinates (x, y) of (0.40, 0.48). To the best of our knowledge, this is one of the highest performing single-doped white organic light-emitting diodes.

키워드