Regiochemistry of donor dendrons controls the performance of thermally activated delayed fluorescence dendrimer emitters for high efficiency solution-processed organic light-emitting diodes

Dianming Sun, Rishabh Saxena, Xiaochun Fan, Stavros Athanasopoulos, Eimantas Duda, Ming Zhang, Sergey Bagnich, Xiao-Hong Zhang, Eli Zysman-Colman*, Ann Koehler

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

The potential of dendrimers exhibiting thermally activated delayed fluorescence (TADF) as emitters in solution-processed organic light-emitting diodes (OLEDs) has to date not yet been realized. This in part is due to a poor understanding of the structure–property relationship in dendrimers where reports of detailed photophysical characterization and mechanism studies are lacking. In this report, using absorption and solvatochromic photoluminescence studies in solution, the origin and character of the lowest excited electronic states in dendrimers with multiple dendritic electron-donating moieties connected to a central electron-withdrawing core via a para- or a meta-phenylene bridge is probed. Characterization of host-free OLEDs reveals the superiority of meta-linked dendrimers as compared to the already reported para-analogue. Comparative temperature-dependent time-resolved solid-state photoluminescence measurements and quantum chemical studies explore the effect of the substitution mode on the TADF properties and the reverse intersystem crossing (RISC) mechanism, respectively. For TADF dendrimers with similarly small ∆EST, it is observed that RISC can be enhanced by the regiochemistry of the donor dendrons due to control of the reorganization energies, which is a heretofore unexploited strategy that is distinct from the involvement of intermediate triplet states through a nonadiabatic (vibronic) coupling with the lowest singlet charge transfer state.
Original languageEnglish
Article number2201470
Number of pages13
JournalAdvanced Science
Volume9
Issue number20
Early online date25 Apr 2022
DOIs
Publication statusPublished - 15 Jul 2022

Keywords

  • TADF dendrimers
  • Triazine
  • Carbazole
  • External quantum efficiency
  • OLEDs
  • Solution-processing

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