Improving processability and efficiency of Resonant TADF emitters: a design strategy

David Hall, Subeesh Madayanad Suresh, Paloma Lays dos Santos, Eimantas Duda, Sergey Bagnich, Anton Pershin, Rajamalli Pachai Gounder, David Bradford Cordes, Alexandra Martha Zoya Slawin, David Belijonne, Anna Köhler, Ifor David William Samuel, Yoann Olivier, Eli Zysman-Colman

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)

Abstract

A new design strategy is introduced to address a persistent weakness with resonance thermally activated delayed fluorescence (R-TADF) emitters to reduce aggregation-caused quenching effects, which we identify as one of the key limiting factors. The emitter Mes3DiKTa shows an improved photoluminescence quantum yield of 80% compared to 75% for the reference DiKTa in 3.5 wt% mCP. Importantly, emission from aggregates, even at high doping concentrations, is eliminated and aggregation-caused quenching is strongly curtailed. For both molecules, triplets are almost quantitatively upconverted into singlets in electroluminescence, despite a significant (~0.21 eV) singlet-triplet energy gap (ΔEST), in line with correlated quantum-chemical calculations, and a slow reverse intersystem crossing. We speculate that the lattice stiffness responsible for the narrow fluorescence and phosphorescence emission spectra also protects the triplets against non-radiative decay. An improved EQEmax of 21.1% for Mes3DIKTa compared to the parent DiKTa (14.7%) and, importantly, reduced efficiency roll- off compared to literature resonance TADF OLEDs, shows the promise of this design strategy for future design of R-TADF emitters for OLED applications.
Original languageEnglish
Article number1901627
JournalAdvanced Optical Materials
VolumeEarly View
Early online date3 Dec 2019
DOIs
Publication statusE-pub ahead of print - 3 Dec 2019

Keywords

  • Blue emission
  • Multiresonance thermally activated delayed fluorescence
  • Organic light emitting diodes
  • SCS-CC2 approach

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