High efficiency organic light-emitting diodes with yellow phosphorescent emission based on a novel iridium complex

Multilayer phosphorescent organic light-emitting diodes with bright yellow light emission based on novel bis[2-(4-tert-butylphenyl) benzothiazolato-N,C 2′ ] iridium (acetylacetonate) [(t-bt) 2 Ir(acac)] were fabricated. The device structure is ITO/CuPc (15 nm)/NPB (15 nm)/CBP: (t-bt) 2 Ir(acac) (5 wt%, 30 nm)/BCP (20 nm)/Alq (20 nm)/LiF (1nm)/Al (100 nm). Electroluminescent (EL) spectra of the device have a main peak at 560 nm with a shoulder at 596 nm ascribed to (t-bt) 2 Ir(acac) phosphor and a weak peak from the NPB layer. A maximum luminance of 10 500 cd m −2 at a driving voltage of 12.5 V and current density of 188 mA cm −2 and a maximum external quantum efficiency of 6.1% at 4.2 V were achieved.