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-Alq(3) co-host emission layer was fabricated. From electroluminescence (EL) measurements, it was found not only that the residual emission from Alq(3) affected the emission color and emission stability of the device but also that the residual Alq(3) emission was reduced by the addition of Rubrene and C6 sensitizers. Rubrene doping increased both the luminance intensity and current density of the device by a factor of 2.0, whereas C6 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/cm(2), the decrease in EL efficiency was less than 10.8%. The variations (Delta x, Delta y) 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). (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.046112jes] All rights reserved.