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Issue 27, 2019
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Turn on of sky-blue thermally activated delayed fluorescence and circularly polarized luminescence (CPL) via increased torsion by a bulky carbazolophane donor

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Abstract

The carbazolophane (Czp) donor unit (indolo[2.2]paracyclophane) is introduced to the design pool of donors in thermally activated delayed fluorescence emitters. The increased steric bulk of the annelated donor unit forces an increased torsion between the carbazole and the aryl bridge resulting in a decreased ΔEST and an enhancement of the thermally activated delayed fluorescence in the triazine-containing emitter CzpPhTrz. Further, the closely stacked carbazole and benzene units of the paracyclophane show through-space π–π interactions, effectively increasing the spatial occupation for the HOMO orbital. The chiroptical properties of enantiomers of [2.2]paracyclophane reveal mirror image circular dichroism (CD) and circularly polarized luminescence (CPL) with glum of 1.3 × 10−3. rac-CzpPhTrz is a sky-blue emitter with λPL of 480 nm, a very small ΔEST of 0.16 eV and high ΦPL of 70% in 10 wt% doped DPEPO films. Sky blue-emitting OLEDs were fabricated with this new TADF emitter showing a high maximum EQE of 17% with CIE coordinates of (0.17, 0.25). A moderate EQE roll-off was also observed with an EQE of 12% at a display relevant luminance of 100 cd m−2. Our results show that the Czp donor contributes to both a decreased ΔEST and an increased photoluminescence quantum yield, both advantageous in the molecular design of TADF emitters.

Graphical abstract: Turn on of sky-blue thermally activated delayed fluorescence and circularly polarized luminescence (CPL) via increased torsion by a bulky carbazolophane donor

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Publication details

The article was received on 12 Apr 2019, accepted on 28 May 2019 and first published on 29 May 2019


Article type: Edge Article
DOI: 10.1039/C9SC01821B
Chem. Sci., 2019,10, 6689-6696
  • Open access: Creative Commons BY-NC license
    All publication charges for this article have been paid for by the Royal Society of Chemistry

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    Turn on of sky-blue thermally activated delayed fluorescence and circularly polarized luminescence (CPL) via increased torsion by a bulky carbazolophane donor

    N. Sharma, E. Spuling, Cornelia M. Mattern, W. Li, O. Fuhr, Y. Tsuchiya, C. Adachi, S. Bräse, I. D. W. Samuel and E. Zysman-Colman, Chem. Sci., 2019, 10, 6689
    DOI: 10.1039/C9SC01821B

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