High-brightness, high-color-purity, white organic light-emitting diodes featuring multiple emission layers

Abstract

We have developed high-brightness, high-color-purity, white organic light-emitting diodes featuring three emission layers: (i) the green light-emitting material 1,3,5-tris(1-pyrenyl)benzene (TPB3), (ii) the host material 1,4-bis(2,2-diphenylvinyl)biphenyl (DPVBi) doped with the blue dye di(4-fluorophenyl)amino-di(styryl)biphenyl (DSB), and (iii) tris(8-hydroxyquinoline)aluminum (Alq3) doped with the red dye 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB). A device having the configuration indium tin oxide (1300 Å)/N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (500 Å)/TPB3 (200 Å)/DPVBi: 2 wt % DSB (150 Å)/Alq3: 2 wt % DCJTB (150 Å)/Alq3 (350 Å)/LiF (8 Å)/Al (2000 Å) exhibited a white emission with a maximum luminance at 15 V of 55 800 cd/m2, a maximum current efficiency of 4.06 cd/A at 13 V, a maximum power efficiency of 2.24 lm/W at 5 V, and a maximum external quantum efficiency of 2.45% at 5 V. The Commission Internationale de l’Eclairage coordinates of (0.33, 0.32) changed only slightly upon varying the potential from 9 to 13 V. We attribute the high brightness and color purity of the emitted white light to the high electroluminescence of the hosts and dopants, the relatively high efficiency of the energy transfer from the hosts to the dopants, and the high control over the thicknesses and dopant concentrations of the red-, green-, and blue-emitting layers, resulting in suitable numbers of partial excitons being generated in each of those three layers.