Meta-linked CBP-derivatives as host materials for a blue iridium carbene complex

Abstract We present four derivatives of 4,4′-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 °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.

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