Efficient white organic light‐emitting diodes based on a balanced split of the exciton‐recombination zone using a graded mixed layer as an electron‐blocking layer

Abstract

Abstract— Efficient white organic light‐emitting diodes with both a graded mixed layer as the blue‐emitting layer and an electron‐blocking layer, and a DPVBi:Rubrene layer as a yellow‐emitting layer have been demonstrated. The mixing of the two colors occurs due to a balanced split of the exciton‐recombination zone by the graded mixed layer serving as the electron‐blocking layer. The white organic light‐emitting diode with an ITO/2‐TNATA 30 nm/NPB 30 nm/DPVBi:Rubrene (1.0 wt.%) 5 nm/NPB:DPVBi (9:1) 150 nm/NPB:DPVBi (5:5) 75 nm/NPB:DPVBi (3:7) 75 nm/NPB:DPVBi (2:8) 75 nm/NPB:DPVBi (0.5:9.5) 75 nm/BCP 5 nm/Alq3 30 nm/LiF 0.5 nm/Al 100 nm structure is chosen as a device with an optimal configuration among devices investigated in this study. The employment of the graded mixed layer in the device is effective in suppressing the color shift at different voltages. The white light, with a Commission Internationale d'Eclairage chromaticity coordinates of (0.33, 0.34), is obtained with an applied voltage of 10.5 V for the device. At the applied voltage, the luminance is 4882 cd/m2 and the current efficiency is 5.03 cd/A.