Deep-blue phosphorescent iridium(III) dyes based on fluorine-functionalized bis(2,3 '-bipyridyl) ligand for efficient organic light-emitting diodes

摘要

Four blue phosphorescent complexes with the general formula (4-R-dfpypy)2Ir(L<^>X), where 4-Rdfpypy 4-alkyl-2',6'-difluoro-2,3'-bipyridine and L<^>X = picolinate or dipivaloylmethanate, were synthesized, and their photoluminescent properties were systematically investigated. All complexes show bright deep-blue phosphorescence emissions with lambda(max) = 440-450 nm and quantum efficiencies of 0.25 - 0.78 in the fluid state. The emission bands of compounds 1-4 are slightly red shifted by 5-10 nm relative to the homoleptic congener, Ir(dfpypy)3. Electroluminescent (EL) devices were fabricated using compound 2 as a dopant, 1,3-bis(N-carbazolyl)benzene (mCP) as the host, and TSPO1 (diphenylphosphineoxide-4-(triphenylsilyl)phenyl) as the electron transporting/exciton blocking layer. These EL devices show a deep-blue color (CIE: x, y = 0.14, 0.17) with high efficiencies. The EL device of compound 2 at a doping level of 5 wt% has the best performance with an EQE of 14.6% at a brightness of 100 cd/m(2) and a current efficiency of 18.3 cd/A. (C) 2015 Elsevier Ltd. All rights reserved.