N,N'-dicarbazolyl-4,4'-biphenyl (CBP) is one of the most widely used organic semiconductors used as hosts for phosphorescent dopants in organic light-emitting diodes (OLEDs). One of the key requirements for OLED hosts is also that their triplet energy be =0.2 eV to prevent dopant-to-host back energy transfer. The ET corresponding to blue phosphorescence in dopants is ET  2.7-2.8 eV (?max 440-460 nm), thus hosts with ET  =2.8 eV are desired. The CBPET =2.56 eV. CBP is a 4,4'-substituted biphenyl derivative. The DFT-aided design suggested the CBP isomers to have significantly higher triplet energies. Albeit more difficult to synthesize, the isomers indeed display high triplet energies ET  2.75-3.02 eV, retain the conductivity and processability of the parent CBP. The HOMO-LUMO gap increased as a result of changes in both HOMO and LUMO levels. The novel materials can efficiently host blue phosphorescent dopants without quenching the emission and afford blue electrophosphorescence in blue-light emitting OLEDs.

N, N'-dicarbazolyl-4,4'-biphenyl (CBP) isomers with high triplet energies as hosts for blue phosphorescence: Synthesis, spectroscopy, and OLEDs

240th National Meeting (2010)

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