Efficient triplet exciton confinement of white organic light-emitting diodes using a heavily doped phosphorescent blue emitter

Abstract

We demonstrated efficient white electrophosphorescence with a heavily doped phosphorescent blue emitter and a triplet exciton blocking layer (TEBL) inserted between the hole transporting layer (HTL) and the emitting layer (EML). We fabricated white organic light-emitting diodes (WOLEDs) (devices A, B, C, and D) using a phosphorescent red emitter; bis(2-phenylquinolinato)-acetylacetonate iridium III (Ir(pq)(2)acac) doped in the host material; N,N'-dicarbazolyl-3,5-benzene (mCP) as the red EML and the phosphorescent blue emitter; bis(3,5-Difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl) iridium III (FIrpic) doped in the host material; p-bis(triphenylsilyly)benzene (UGH2) as the blue EML The properties of device 8, which demonstrate a maximum luminous efficiency and external quantum efficiency of 26.83 cd/A and 14.0%, respectively, were found to be superior to the other WOLED devices. It also showed white emission with CIExy coordinates of (x = 0.35, y = 0.35) at 8 V. Device D, which has a layer of P-type 4,4',4 ''-tri(N-carbazolyl) triphenylamine (TCTA) material between the HTL and TEBL, was compared with device A to determine the 430 nm emission peak. (C) 2010 Elsevier B.V. All rights reserved.