Highly Efficient Phosphorescent White Organic Light-Emitting Devices with a Poly(N-vinylcarbazole) Host Layer

Abstract

We have fabricated phosphorescent white organic light-emitting devices (WOLEDs) with a spin-coated poly(Nvinylcarbazole) [PVK] host layer. Iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,<TEX>$C^{2'}$</TEX>]picolinate (FIrpic), tris(2-phenylpyridine)iridium(III) [<TEX>$Ir(ppy)_3$</TEX>], and tris(2-phenyl-1-quinoline)iridium(III) [<TEX>$Ir(phq)_3$</TEX>], were used as the blue, green, and red guest materials, respectively. The PVK was mixed with FIrpic, <TEX>$Ir(ppy)_3$</TEX>, and <TEX>$Ir(phq)_3$</TEX> molecules in a chlorobenzene solution and spin-coated in order to prepare the emission layer; 3-(4-biphenylyl)-4-phenyl-5-(4-tertbutylphenyl)-1,2,4-triazole (TAZ) was used as an electron transport material. The resultant device structure was ITO/PVK:FIrpic:<TEX>$Ir(ppy)_3:Ir(phq)_3$</TEX>/TAZ/LiF/Al. The electroluminescence, efficiency, and electrical conduction characteristics of the WOLEDs based on the doped PVK host layer were investigated. The maximum current efficiency of the three wavelength WOLED with the doped PVK host was 19.2 cd/A.