Schrögel, P.; Langer, N.; Schildknecht, Ch.; Wagenblast, G.; Lennartz, Ch.; Strohriegl, P.: Meta-linked CBP-derivatives as host materials for a blue iridium carbene complex, Organic Electronics, 12(11), 2047-2055 (2011) -- DOI: 10.1016/j.orgel.2011.08.012 | |
Abstract: We present four derivatives of 4,40-bis(9-carbazolyl) biphenyl (CBP) for the use as host materials in blue phosphorescent organic light emitting diodes. By replacing the para-linkage by a meta-linkage of the carbazole substituents at the central biphenyl unit materials with improved thermal and optical properties are obtained. The triplet energy of the meta-linked host materials is significantly increased to more than 2.90 eV compared to 2.58 eV for the para-linked CBP. Moreover, selective methyl substitution of the basic meta-CBP structure leads to materials with high glass transition temperatures up to 120 degrees C and electrochemical stability of the oxidised species against dimerisation. The high triplet energy allows the use of the meta-CBP derivatives as host materials for the carbene emitter mer-tris(N-dibenzofuranyl-N'-methylimidazole) iridium (III) (Ir(dbfmi)) with a pure blue emission at 450 nm. (C) 2011 Elsevier B. V. All rights reserved. |