Nam-Soo Kim

High efficiency green phosphorescent OLEDs with long lifetime by using novel host material

We developed a novel host material, CheilGH-01 reinforced with electron transporting property to perform high luminance efficiency and low driving voltage with long lifetime in green phosphorescent OLED without HBL (hole blocking layer). The device with a structure of ITO/NPB/TCTA/Host:Ir(ppy)3/Balq/Alq3/Liq/Al using CheilGH-01 as a host showed better performance than the device with CBP as a host; At luminance of 1000 cd/m2, driving voltages, current efficiencies and power efficiencies are 5.4 V, 60 cd/A and 35 lm/W for CheilGH-01 and 7.2 V, 42 cd/A and 18.8 lm/W for CBP. It takes 240 hours for CheilGH-01 and 177 hours for CBP from the initial luminance of 3000 cd/m2 to the luminance of 1500 cd/m2 (55% of the initial). In the case of device with a structure of ITO/NPB/TCTA /Host:Ir(ppy)3/Alq3/Liq/Al, CheilGH-01 showed 300% enhancement in luminance efficiency and more than 800% longer lifetime than CBP; At luminance of 1000 cd/m2, driving voltages, current efficiencies and power efficiencies are 6.3 V, 51 cd/A and 26 lm/W for CheilGH-01 and 8.6 V, 21 cd/A and 7.8 lm/W for CBP. It takes 411 hours for CheilGH-01 and 82 hours for CBP from the initial luminance of 3000 cd/m2 to the luminance of 1500 cd/m2. By using our novel host material, we are able to eliminate HBL from the conventional green phosphorescent OLED and still provide OLED with longer lifetime and excellent luminance efficiency.