High efficiency white organic light emitting diodes using Rubrene doped N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine as an emitting layer

A bright white organic light emitting diode (WOLED) was fabricated in which a blue light emitting host NPB was doped with a tiny yellow dopant Rubrene. The device structure was ITO/NPB:Rubrene/BCP/Alq3/LiF/Al, where NPB is N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine, Rubrene is 5,6,11,12-tetraphenylnaphthacene, BCP is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, and Alq3 is tris(8-hydroxyquinoline) aluminum. White light emission was realized in an OLED with 2 % Rubrene doping concentration. A maximum luminance of 13550 cd/m² and a power efficiency of 2.8 lm/W (7.9 cd/A) were obtained in the device. The Commission Internationale De L'Eclairage (CIE) (1931) coordinates of the white emission are well within the white zone, which moves from (0.35, 0.37) to (0.33, 0.35) when the applied voltage is varied from 6 V to 14 V.