Improvements in Color Purity and Stability of Red OLEDs by Sensitizer Doping

Abstract

This paper demonstrates how sensitizer doping improves the color purity and emission stability of a red organic light-emitting diode (OLED). A device with an MADN–Alq3 co-host emission layer was fabricated. From electroluminescence (EL) measurements, it was found not only that the residual emission from Alq3 affected the emission color and emission stability of the device but also that the residual Alq3 emission was reduced by the addition of Rubrene and 6, sensitizers. Rubrene doping increased both the luminance intensity and current density of the device by a factor of 2.0, whereas 6, doping increased the luminance intensity by a factor of 1.3 and the current density by a factor of 1.2. When the current density was increased from 10 to 132 mA/cm2, the decrease in EL efficiency was less than 10.8%. The variations (Δx, Δy) in the CIE coordinates were (0.02, 0.01) for the device doped with Rubrene and (0.01, 0.01) for that doped with C6. The maximum EL efficiency was 5.28 cd/A, and the CIE coordinates were (0.63, 0.36).