Non-doped white organic light-emitting diodes consisting of three primary colors based on a bipolar emitter

White organic light-emitting diodes (WOLEDs) with non-doped structure have been fabricated using an bipolar fluorescent material of 2-{4-[bis(9,9-dimethylfluorenyl)amino]phenyl}-5-(dimesityl boryl)thiophene (FlAMB-1T) as both hole-electron transporting and green light-emitting layer. An ultrathin layer of 3-(dicyanomethylene)-5,5-dimethyl-1-(4-dimethylamino-styryl) cyclohexene (DCDDC) was inserted between two FlAMB-1T layers as a red light-emitting layer and a thin 4,4′-bis(2,2′-diphenyvinyl)-1,1′-dipenyl (DPVBi) as a blue light-emitting layer. The thickness of the FlAMB-1T determined the device spectrum, and enabled a white emission to be achieved. A fairly pure WOLED with Commission Internationale De L’Eclairage (CIE) coordinates of (0.33, 0.36) consisting of three primary colors was obtained. The emission mechanisms of DCDDC and the role of FlAMB-1T bipolar material in the WOLED was discussed.

► WOLEDs with non-doped structure were fabricated using three primary colors.
► A new bipolar emitter of FlAMB-1T is innovatively introduced into the non-doped WOLEDs.
► The recombination zone is dominated by the thickness of the second FlAMB-1T layer.