Emitting-layer design of white organic light-emitting devices with single-host material
Journal
Journal of Applied Physics
Journal Volume
106
Journal Issue
2
Date Issued
2009
Author(s)
Hsiao, C.-H.
Abstract
Efficient phosphorescence sensitization (PS) consisting of tris(phenylpyridine)iridium (Ir (ppy) 3) sensitizers and 4-(dicyanomethylene)-2- t -butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)- 4H -pyran) (DCJTB) exciton acceptors in a host material, N, N′ -dicarbazolyl-3,5-benzene, was implemented by a simplified emitting-layer structure with selectively doped DCJTB in the Ir (ppy) 3 -doped region. This codoped region away from the recombination zone peak in the Ir (ppy) 3 -doped region significantly improved the PS efficiency without affecting the carrier transport characteristics. Coupled with an efficiently phosphorescent blue emitter, iridium(III)bis[(4,6-di-fluoropheny)- pyridinato- N, C 2′] picolinate, a white organic light-emitting device utilizing this PS approach was demonstrated to have 10.94% external quantum efficiency, 17.4 cd/A and 12.2 lm/W at an applied voltage of 4.5 V, and a brightness of 107 cd/ m2 with Commission Internationale de l'Eclairage coordinates of (0.293, 0.427). With a 3 nm spacer for manipulating the exciton diffusion in the emitting layer, a slight CIE coordinates variation of (-0.008, -0.006) was obtained at practical luminance levels of 1000-4000 cd/ m2, evidence that PS was successfully achieved. © 2009 American Institute of Physics.
Type
journal article