Relationship between host energy levels and device performances of phosphorescent organic light-emitting diodes with triplet mixed host emitting structure

Abstract

Green phosphorescent organic light-emitting diodes ͑PHOLEDs͒ with a triplet mixed host emitting layer were developed and device performances were studied by changing host materials in light-emitting layer. Power efficiency of green PHOLEDs could be improved from 12.7 to 29.1 lm/ W by using triplet mixed host emitting layer. Combination of hole-transport-type host with good hole injection properties and electron-transport-type host with good electron injection properties was effective to get high efficiency in triplet mixed host devices.

2‐Diphenylaminofluoren‐7‐ylstyrene Derivatives with Various Aromatic End‐Capping Groups for Highly Efficient Blue and White Organic Light‐Emitting Diodes

“…All devices showed high EQEs from 4.38 to 6.20 % that almost exceeded the theoretical limits of the fluorescent OLEDs. [30][31][32] Furthermore, the blue-emitting devices exhibited little efficiency fall-off, even though the current density had increased. At more than the practical luminance of 10000 cd m -2 , the luminous efficiencies of all devices decreased slightly (3-13 %).…”

On the triplet distribution and its effect on an improved phosphorescent organic light-emitting diode

“…When the Ir(ppy) 3 doping was moved towards the cathode side, however, we observed an additional blue emission with a peak around 460 nm, which corresponds to the emission of NPB. 20 Furthermore, an increase in NPB emission is observed as the Ir(ppy) 3 doping was moved away from the NPB/CBP interface. We can conclude that majority of excitons are formed at the NPB/CBP interface.…”

28.3: Invited Paper: Progress on Phosphorescent OLED Materials

“…Much work has been done to improve the luminance efficiency of phosphorescent OLEDs through the development of materials and device structures [2,3]. Despite the improvement in efficiencies of these phosphorescent OLEDs, their operational lifetimes are the key issues for real applications.…”