Effect of Substituents on the Electronic Structure and Degradation Process in Carbazole Derivatives for Blue OLED Host Materials

Minki Hong, Mahesh Kumar Ravva, Paul Winget, Jean-Luc Bredas

Research output: Contribution to journalArticlepeer-review

75 Scopus citations

Abstract

We investigate the dissociation mechanism of the C-N bond between carbazole and dibenzothiophene in carbazole-dibenzothiophene (Cz-DBT) positional isomers, selected as representative systems for blue host materials in organic light-emitting diodes (OLEDs). The C-N bond dissociation energies, calculated at the density functional theory level, are found to depend strongly on the charge states of the parental molecules. In particular, the anionic C-N bond dissociations resulting in a carbazole anion can have low dissociation energies (∼1.6 eV) with respect to blue emission energy. These low values are attributed to the large electron affinity of the carbazole radical, a feature that importantly can be modulated via substitution. Substitution also impacts the energies of the first excited electronic states of the Cz-DBT molecules since these states have an intramolecular charge-transfer nature due to the spatially localized character of the frontier molecular orbitals within the carbazole moiety (for the HOMO) and the dibenzothiophene moiety (for the LUMO). The implications of these results must be considered when designing blue OLED hosts since these materials must combine chemical stability and high triplet energy. © 2016 American Chemical Society.
Original languageEnglish (US)
Pages (from-to)5791-5798
Number of pages8
JournalChemistry of Materials
Volume28
Issue number16
DOIs
StatePublished - Aug 3 2016

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported by King Abdullah University of Science and Technology and in part at the Georgia Institute of Technology by the Global Research Outreach (GRO) Program of the Samsung Advanced Institute of Technology (SALT). We acknowledge the IT Research Computing Team and Super computing Laboratory at KAUST for providing computational and storage resources. We thank Dr. Gjergji Sini for insightful discussions.

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