Structure-property relationship in high triplet energy host materials with a phenylcarbazole core and diphenylphosphine oxide substituent

A series of high triplet energy host materials with a carbazole core and a diphenylphosphine oxide substituent were synthesized and the effect of the substitution position on the photophysical properties and device performances of the host material was investigated. The substitution position of the diphenylphosphine oxide on the phenyl ring was changed and the substitution at ortho position of the phenyl ring induced the intramolecular charge transfer complex formation. The intramolecular charge transfer complex formation in the ortho substituted compound improved the current density. A maximum quantum efficiency of 20.4% was obtained in the phenylcarbazole host material with the phosphine oxide at para position of the phenyl group and the efficiency was degraded in the ortho substituted host. (C) 2011 Elsevier B.V. All rights reserved.