Highly Efficient Orange Phosphorescent Organic Light Emitting Diodes with Reduced Roll-Off Using Xanthene-Conjugated...

The development of high-efficiency orange phosphorescent organic light-emitting diodes (PhOLEDs) with reduced efficiency roll-off offers significant benefits, enabling a more simplified method for producing white-OLEDs through the combination of sky blue and orange OLEDs, in contrast to the conventional use of three primary colors. Herein, we have designed and synthesized two hosts with 9-(4-(14H-dibenzo[a,j]xanthen-14-yl)phenyl)-9H-carbazole (XaPCz) and 10-(4-(14H-dibenzo[a,j]xanthen-14-yl)phenyl)acridin-9(10H)-one (XaPAc) derivatives. The singlet and triplet energies for XaPCz and XaPAc are S₁=3.65, 3.12 eV, and T₁=2.67, 2.70 eV, respectively. These materials are employed as hosts for orange PhOLEDs using bis(2-phenylquinoline) (acetylacetonate) iridium (III) [Ir(pq)₃] as an emitter. XaPCz demonstrates maximum external quantum efficiency (EQE_max) of 20.5 %, and XaPAc shows EQE_max of 22.3 % with Commission Internationale de l'Eclairage (CIE) coordinates of (0.53, 0.46) and (0.54, 0.45), respectively. In addition, the XaPAc-based device shows a lower turn-on voltage (2.5 V) and high-power efficiency of 60.0 lm/W. More importantly, both device shows reduced roll-off and retain more than 94 % of EQE_max at 1,000 cd/m². The XaPAc-based device maintains an EQE of 17.9 % even at 10,000 cd/m².