A novel orange-red phosphorescent iridium complex PR-24 has been successfully synthesized and characterized. By using this material, we demonstrated the high-efficiency OLED devices. The best efficiency was achieved for a device using PR-24 as the dopant, exhibiting 25.8 cd/A current efficiency, 20.0 lm/W power efficiency and 15.9% EQE at 1000 cd/m2 . Moreover, when using the optimized co-host configuration, PR-24 shows a remarkable lifetime T<sub>50</sub> of 211,000 h for an initial luminance of 1000 nits .
A new type of thiopyridinyl-based iridium molecule (POT) was used as the yellow phosphorescent material in our research. On fabricating a yellow PHOLED by doping POT-02 with host as the emitter, the device achieved a high power efficiency of 66.0 lm/W and an external quantum efficiency of 23.2%. On the other hand, a white organic lightemitting diode (WOLED) with a high power efficiency has been demonstrated by dispersing a host-free, yellow phosphorescent material in-between double blue phosphorescent emitters. In this study, we introduce a simple process for generating yellow emission of a WOLED by using the B/Y/B EML configuration. The B/Y/B EML configuration can achieve a higher efficiency and a smaller color shift with various operational brightness values. Based on the concept of this device, the molecular engineering of the blue phosphorescent host material as well as the light-extraction film, a WOLED with a power efficiency of 103 lm/W and an external quantum efficiency of 38.2% at a practical brightness of 1000 cd/m<sup>2</sup> with CIE coordinates (CIE<sub>x, y</sub>) of (0.36, 0.48) can be achieved.
A series of novel thieno[3,2-c]pyridine-based RGBY phosphorescent Ir complexes have been synthesized and characterized. Solution-processable double-layered OLEDs fabricated with theses materials as the light-emitting layer exhibit high efficiencies. The monochromatic large-area of 40 x 83 mm<sup>2</sup> Yellow and Green OLEDs have also been demonstrated.
The solution/evaporation hybrid processed organic light emitting devices composed of newly developed host material
CzDBS, green PG-02 dopant, and orange PO-01-TB and PO-06 dopants are studied. Orange, green and two-peak white
light emitting devices were fabricated by using spin coating of HIL, HTL and emission layers followed by thermal
evaporation of ETL and cathode. The orange devices achieved efficacies of 26.9 cd/A and 14.6 lm/W at the brightness of
1538 nits. The green devices, on the other hand, achieved efficacies of 31.3 cd/A and 19.7 lm/W at the brightness of
1590 nits. The two-peak white devices, composed of blue FIrpic and orange PO-01-TB, achieved efficacies of 36.9 cd/A
and 18.4 lm/W at the brightness of 1150 nits.