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Thermally activated delayed fluorescence emitters with dual conformations for white organic light-emitting diodes: mechanism and molecular design

Abstract

Thermally activated delayed fluorescence (TADF) molecules with dual emission are of great potential to be used as single emitters in white organic light-emitting diodes (WOLEDs). In this paper, the light-emitting mechanisms of PTZ-TTR and PTZ-Ph-TTR with blue-orange dual emission are studied systematically. The near-planar and near-orthogonal conformations are responsible for the blue and orange emission respectively. For PTZ-TTR, the near-orthogonal conformation is only generated by the transformation from the near-planar conformation, while the near-orthogonal conformation of PTZ-Ph-TTR can be generated by both excitation and transformation. This results in relative strong orange emission in PTZ-Ph-TTR. In addition, the TADF mechanism is investigated, and two up-conversion pathways are revealed for both molecules. Based on the comparison of the photophysical properties of PTZ-TTR in toluene and aggregation state, we find that aggregation could induce a smaller energy gap between the first singlet excited state and the first triplet excited state. Besides, the substitution effect of donors on the light-emitting properties is studied, and the design rules for emitters with dual conformation and compensatory emission are proposed. Our theoretical results would favor the understanding of the light-emitting mechanism as well as the design of new-type TADF emitters in WOLEDs.

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Supplementary files

Publication details

The article was received on 11 Oct 2019, accepted on 29 Nov 2019 and first published on 30 Nov 2019


Article type: Paper
DOI: 10.1039/C9CP05552E
Phys. Chem. Chem. Phys., 2019, Accepted Manuscript

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    Thermally activated delayed fluorescence emitters with dual conformations for white organic light-emitting diodes: mechanism and molecular design

    F. Li, G. Jiang, M. Li, J. Fan, Y. Song, C. Wang and L. Lin, Phys. Chem. Chem. Phys., 2019, Accepted Manuscript , DOI: 10.1039/C9CP05552E

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