PNNL

Abstract

We have demonstrated high-efficiency turquoise-blue electrophosphorescence from the complex Pt(ptp)2 = bis[3,5–bis(2–pyridyl)–1,2,4–triazolato]platinum(II) doped in the wide band-gap, ambipolar phosphine oxide host HM-A1 = 4-(diphenylphosphoryl)-N,N-diphenylaniline. For devices with 5% Pt(ptp)2 doping in HM-A1, we have achieved a peak external quantum efficiency and power efficiency of (11.8 ± 0.6) % and (61.2 ± 5.9) lm/W with high-pixel values of 13.1 % and 70.6 lm/W, respectively. These parameters maintained (10.6 ± 0.2) % and (40.3 ± 1.2) lm/W at a brightness of 1000 cd/m2 with high-pixel values of 10.8 % and 41.6 lm/W. Examination of several device structures suggests that the high performance is due to improved charge transport and exciton confinement in the emissive region. Devices with 1-10% doping concentration exhibit turquoise-blue emissions (?max ~ 480 nm) with a monotonic decrease in monomer/excimer intensity ratio upon increasing the doping concentration. Devices with 5% doping exhibit sufficient blue contribution to attain white light upon combination with highly-doped or neat emissive layers of the same phosphor; the work herein represents a significant backdrop toward optimizing such white OLEDs given the performance metrics above, which to our knowledge represent the highest performance for OLEDs that exhibit blue emission maxima.