Thermally activated and aggregation-regulated excitonic coupling enable emissive high-lying triplet excitons

Tao Wang, Joydip De, Sen Wu, Abhishek Kumar Gupta, Eli Zysman-Colman*

*Corresponding author for this work

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Abstract

Room-temperature phosphorescence (RTP) originating from higher-lying triplet excitons remains a rather rarely documented occurrence for purely organic molecular systems. Here, we report two naphthalene-based RTP luminophores whose phosphorescence emission is enabled by radiative decay of high-lying triplet excitons. In contrast, upon cooling the dominant phosphorescence originates from the lowest-lying triplet excited state, which is manifested by a red-shifted emission. Photophysical and theoretical studies reveal that the unusual RTP results from thermally activated excitonic coupling between different conformations of the compounds. Aggregation-regulated excitonic coupling is observed when increasing the doping concentration of the emitters in poly(methylmethacrylate) (PMMA). Further, the RTP quantum efficiency improves more than 80-fold in 1,3-bis(N-carbazolyl)benzene (mCP) compared to that in PMMA. This design principle offers important insight into triplet excited state dynamics and has been exploited in afterglow-indicating temperature sensing.
Original languageEnglish
Article numbere202206681
Number of pages11
JournalAngewandte Chemie International Edition
Volume61
Issue number33
Early online date4 Jul 2022
DOIs
Publication statusPublished - 8 Aug 2022

Keywords

  • Excitonic coupling
  • Higher-lying triplet excitons
  • Host-guest system
  • Room-temperature phosphorescence

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