All-phosphorescent three-color two-stack tandem white organic light emitting diodes with high-color-rendering index values

摘要

Reported herein are high-color-rendering index two-stack phosphorescent tandem white organic light-emitting diodes using three-color phosphorescent dopants: iridium(III) bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl) (472?nm) as a blue emitter for the first stack layer, and iridium(III) bis(4-methyl-2-(3,5-dimethylphenyl)quinolinato-N,C2′) tetramethylheptadionate (612?nm) and iridium(III) bis(4-(4-tbutylphenyl)thieno[3,2-c]pyridinato-N,C2′)acetylacetonate (562?nm) as red and yellow triplet emitters for the second stack layer, respectively. By locating the blue and red emissive layers slightly far from their antinode position in terms of photonic mode density, the electroluminescent spectra could be changed, and the CRI values could be increased from 74 to over 85. There is some efficiency loss, however, from 38.6 to 29.4?lm/W due to the inevitable electrical and optical losses.