Balanced Full-Color White Organic Light-Emitting Devices with Simple Double-Emissive-Layer Structure

Abstract

White organic light-emitting devices (WOLEDs) were realized using a simple four-layer structure to obtain red, green and blue emissions for color mixing. A fluorescent dye of 3-(dicyanomethylene)-5,5-dimethyl-1-(4-dimethylamino-styryl) cyclohexene doped in tris(8-quinolinolato) aluminum matrix and a thin N,N'-bis(1-naphthyl)-N,N'-biphenyl-1,1'-biphenyl-4,4'-diamine layer were constructed to act as the dual emitting layer. The device showed a current efficiency of 5.0 cd/A with a luminance of 2020 cd/m2 and Commission Internationale De L'Eclairage (CIE) coordinates of (0.32, 0.32) at 11.6 V, and a maximum luminance of 12580 cd/m2 at 330 mA/cm2 (17 V). A good color rendering index of 85 was obtained. Three main emission peaks at 440, 530, and 630 nm were steadily balanced with the CIE coordinates near the optimum white point of (0.33, 0.33) over 9 V. This was attributed to the modification of appropriate energy transfer in the doping system and the confinement of the recombination zone within two emitting layers.