Bright White Organic Light-Emitting Diode With Dual Doped Blue and Yellow-Orange Emitting Layers
Bernard Geffroy, Noella Lemaitre, Jeremie Lavigne, Christine Denis, Pascal Maisse and Paul Raimond
Organic Light Emitting Diodes (OLED) are actively considered as potential next generation of solid state lighting sources due to the tremendous progress in device luminous efficiency and the emerging viability as a commercial display technology. A white OLED has been fabricated employing a highly efficient doped blue material and a yellow-orange doped layer as emitting species. The device structure was ITO/CuPc/NPB:rubrene/DPVBi:PR3491/Alq3/LiF/Al. The blue electroluminescent layer is based on a DPVBi (4, 4’-bis(2, 2’-diphenylvinyl)biphenyl) host doped with a derivative of distyryl biphenyl molecule synthesized in the laboratory. White diodes can be obtained by further doping the hole transport layer (NPB) with rubrene, a highly efficient yellow fluorescent molecule.
By properly tuning the doping rate in order to balance the blue and yellow-orange contribution of the diode emission, a fairly pure white light has been obtained with Commission Internationale de l’Eclairage (CIE) chromaticity coordinates of (0.31; 0.34) and external efficiencies of 3.4% and 8.7 cd/A at a current density of 10 mA/cm2. Moreover, the CIE coordinates of the emitted light are quite stable for luminance values ranging from 500 cd/m2 to 5000 cd/m2.