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Persistent Dimer Emission in Thermally Activated Delayed Fluorescence Materials. | LitMetric

AI Article Synopsis

  • Significant changes in color emission of carbazole-based TADF emitters are linked to persistent dimer states in thin films and OLEDs.
  • The photoexcitation of dimer states affects the color purity of photoluminescence and electroluminescence, revealing the importance of sample preparation methods.
  • Understanding dimerization is crucial for the future design of TADF emitters and clarifies discrepancies in previous research on carbazole-based materials.

Article Abstract

We expose significant changes in the emission color of carbazole-based thermally activated delayed fluorescence (TADF) emitters that arise from the presence of persistent dimer states in thin films and organic light-emitting diodes (OLEDs). Direct photoexcitation of this dimer state in 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene () reveals the significant influence of dimer species on the color purity of its photoluminescence and electroluminescence. The dimer species is sensitive to the sample preparation method, and its enduring presence contributes to the widely reported concentration-mediated red shift in the photoluminescence and electroluminescence of evaporated thin films. This discovery has implications on the usability of these, and similar, molecules for OLEDs and explains disparate electroluminescence spectra presented in the literature for these compounds. The dimerization-controlled changes observed in the TADF process and photoluminescence efficiency mean that careful consideration of dimer states is imperative in the design of future TADF emitters and the interpretation of previously reported studies of carbazole-based TADF materials.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6501699PMC
http://dx.doi.org/10.1021/acs.jpcc.9b01458DOI Listing

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