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Persistent dimer emission in thermally activated delayed fluorescence materials

DOI: 10.1021/acs.jpcc.9b01458 DOI Help

Authors: Marc K. Etherington (Durham University) , Nadzeya A. Kukhta (Durham University) , Heather F. Higginbotham (Durham University) , Andrew Danos (Durham University) , Aisha N. Bismillah (Durham University) , David R. Graves (Durham University) , Paul R. Mcgonigal (Durham University) , Nils Haase (Merck KGaA) , Antonia Morherr (Merck KGaA) , Andrei S. Batsanov (Durham University) , Christof Pflumm (Merck KGaA) , Vandana Bhalla (Durham University; Guru Nanak Dev University) , Martin R. Bryce (Durham University) , Andrew P. Monkman (Durham University)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: The Journal Of Physical Chemistry C

State: Published (Approved)
Published: April 2019
Diamond Proposal Number(s): 11145

Open Access Open Access

Abstract: We expose significant changes in emission color of carbazole-based thermally activated delayed fluorescence (TADF) emitters that arise through 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 (4CzIPN) reveals the significant influence of dimer species on the color purity of its photoluminescence and electrolumines-cence. The dimer species is sensitive to the sample preparation method and its enduring presence contributes to the widely reported concentration-mediated redshift in the photoluminescence and electroluminescence of evaporated thin films. This discovery has significant implications on the usability of these, and similar, molecules for OLEDs and explains disparate electroluminescence spectra presented in the literature for these compounds. The significant dimer-ization-controlled changes observed in the TADF process and photoluminescence efficiency mean that careful consid-eration of dimer states is imperative in the design of future TADF emitters and the interpretation of previously reported studies of carbazole-based TADF materials.

Journal Keywords: Thermally activated delayed fluorescence; carbazoles; dimerization; OLEDs; mechanochromism

Diamond Keywords: Organic Light Emitting Diodes (OLEDs)

Subject Areas: Materials, Chemistry

Instruments: I19-Small Molecule Single Crystal Diffraction

Added On: 08/04/2019 11:16


Discipline Tags:

Physical Chemistry Energy Materials Chemistry Materials Science

Technical Tags:

Diffraction Single Crystal X-ray Diffraction (SXRD)