Abstract
Ideal host-guest system for emission in phosphorescent OLEDs with only 1% guest doping condition for efficient energy transfer have been demonstrated in the present investigation. Using a narrow band-gap fluorescent host material, bis(10-hydroxybenzo[h] quinolinato)beryllium complex (Bebq 2), and red dopant bis(2-phenylquinoline)(acetylacetonate)iridium (Ir(phq) 2acac), highly efficient red phosphorescent OLEDs (PHOLEDs) exhibiting excellent energy transfer characteristics with a doping concentration of 1% were developed. Fabricated PHOLEDs show a driving voltage of 3.7 V, maximum current and power efficiencies of 26.53 cd/A and 29.58 lm/W, and a maximum external quantum efficiency of 21%. Minimized electron or hole trapping at the phosphorescent guest molecules and efficient Förster and Dexter energy transfers from the Bebq 2 host singlet and triplet states to the emitting triplet of Ir(phq) 2acac guest appear to be the key mechanism for ideal phosphorescence emission.
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