Thermally activated delayed fluorescence materials based on 3,6-di-tert-butyl-9-((phenylsulfonyl)phenyl)-9H-carbazoles

•A series of materials for thermally activated delayed fluorescence is synthesized.•The structure-property relationships are studied.•The energy gap between singlet and triplet is tuned from 0.39 eV to 0.22 eV.

A series of bipolar materials for thermally activated delayed fluorescence based on 3,6-di-tert-butyl-9-((phenylsulfonyl)phenyl)-9H-carbazoles, is synthesized by Ulmann coupling reactions. In these materials, the 3,6-di-tert-butylcarbazole group is linked at the 3-, 4- position or 3′-, 4′- position of diphenyl sulfone. The effects of the conjugation connectivity on the electronic, photophysical and electrochemical properties of these materials, are studied by extensive UV–vis, fluorescence spectroscopic measurements, cyclic voltammetry and theoretical calculations as well as X-ray crystallographic analysis. The energy gap between singlet and triplet in these materials is tuned from 0.39 eV to 0.22 eV by manipulation of conjugation of the electron donor units.

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