3-(9-carbazolyI)carbazoles and 3,6-Di(9-carbazolyl)carbazoles as effective host materials for efficient blue organic electrophosphorescence

The effect of linking topology on the electronic coupling between monomeric carbozole units of 3-(9-carbazolyl)carbazoles and 3,6-di(9-carbazolyl) carbazoles for effective blue organic electrophospherescence, is discussed. 3,(6),9′-linked oligocarbazoles exhibit suppression of coupling between monomeric units, leading to localized singlet and triplet excitation within one carbazole unit and small reduction in triplet energies compared to the carbazole monomer. The 3,(6),9′-linking create morphologically stable molecule with lower molecular weights, which enhance the electrophospherescence of the material. A family of 3,(6),9′-linked oligocarbazoles with large triplet energies and high morphological stablities exhibit electrophospherescence up to 15%, 31 cd A^-1 and 28 lm W^-1 for efficient blue phosphorescent organic light-emitting devices (OLEDs).