Efficiency Stabilized Deep Blue Organic Light-Emitting Devices with a DPVBi/CBP Step Emitting Layer Operating at Low Voltages

Abstract

The electrical and the optical properties of deep blue organic light-emitting devices (OLED) utilizing a step emitting layer (SEL) consisting of 4,4′-Bis(2,2′-diphenyl-ethen-1-yl)biphenyl (DPVBi) and 4,4′-Bis(carbazol-9-yl)biphenyl (CBP) were investigated. The turn-on voltage of the OLEDs with a SEL was smaller than those of the OLEDs with a CBP or a DPVBi emitting layer. While the efficiency of the OLEDs with a SEL was very stable, regardless of variations in the applied voltage, that of the OLEDs with a CBP or a DPVBi emitting layer varied with the applied voltage. The dominant peak in the electroluminescence spectrum for the OLEDs with a SEL appeared at 455 nm. The Commission Internationale de l'Eclairage chromaticity (CIE) coordinates of the OLEDs with a SEL at 11 V were (0.160, 0.168), which is similar to the CIE coordinates of the CBP layer.