Broad band and white phosphorescent polymer light-emitting diodes in multilayer structure

Abstract

Efficient phosphorescent polymer light-emitting diode with poly(vinylcarbazole) (PVK) doped by two or three iridium complexes in single and bilayer structures are studied. With (tris-(2-4(4-toltyl) phenylpyridine) (Ir(mppy)(3)) as the green emitter and (1-phenylisoquinoline) (acetylacetonate) iridium(III) (Ir(piq)(2)) as the red emitter the efficiency is as high as 23 cd/A with broad band emission from 500 nm to 720 nm. For white emission a second layer is added with blue emitter ((III) bis[(4,-6-di-fluorophenyl-pyridinato)N,C-2] picolinate) (FIrpic) doped in PVK. White light containing three spectral peaks results with efficiency 8.1 cd/A. As the second blue layer is replaced by the fluorescent (poly(9,9-dioctylfluorene)) (PFO) white emission with high color rendering index 86 is achieved. The efficiency is 5.7 cd/A with peak luminance 8900 cd/m(2). For a given iridium complexes ratio the relative intensity of the green and red emission depends sensitively on the second blue layer. (c) 2008 Elsevier B.V. All fights reserved.