Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/37200
Title: Dominant dimer emission provides colour stability for red thermally activated delayed fluorescence emitter
Authors: CARDEYNAELS, Tom 
Etherington, Marc K.
PAREDIS, Simon 
Batsanov, Andrei S.
DECKERS, Jasper 
Stavrou, Kleitos
VANDERZANDE, Dirk 
Monkman, Andrew P.
Champagne, Benoit
MAES, Wouter 
Issue Date: 2022
Publisher: ROYAL SOC CHEMISTRY
Source: JOURNAL OF MATERIALS CHEMISTRY C,
Status: Early view
Abstract: Colour purity and stability in multi-donor thermally activated delayed fluorescence (TADF) emitters has significant implications for commercial organic light-emitting diode (OLED) design. The formation of emissive dimer states in the well-known 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) chromophore at elevated dopant concentrations has recently been confirmed both experimentally and via theoretical calculations, indicating that multi-donor emitters such as 4CzIPN might suffer from a lack of colour stability due to the presence of multiple emissive states. This poses a serious issue for OLED manufacturers. In this work, dithieno[3,2-b:2',3'-d]pyrrole (DTP) is applied as an alternative donor unit in a TADF emitter for the first time. In combination with isophthalonitrile (IPN), the 4CzIPN analogue termed 4DTPIPN is obtained. The strong electron donating nature of the DTP moiety gives rise to a red shift of the emission with respect to that of 4CzIPN. We identify that 4DTPIPN has a very stable emission spectrum throughout all solid-state thin film concentrations and host materials. Rather interestingly, this colour stability is obtained via the formation of dimer/aggregate species that are present even at 0.01 wt% concentration. Unfortunately, the higher colour stability is paired with a low photoluminescence quantum yield, making 4DTPIPN unviable for device applications. Nonetheless, this work shows the importance of dimer contributions, even at dilute doping concentrations. This molecule and study provide important understanding of the aggregation behaviour of small-molecule emitters necessary for the successful application of doped and, especially, non-doped OLED architectures.
Colour purity and stability in multi-donor thermally activated delayed fluorescence (TADF) emitters has significant implications for commercial organic light-emitting diode (OLED) design. The formation of emissive dimer states in the well-known 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) chromophore at elevated dopant concentrations has recently been confirmed both experimentally and via theoretical calculations, indicating that multi-donor emitters such as 4CzIPN might suffer from a lack of colour stability due to the presence of multiple emissive states. This poses a serious issue for OLED manufacturers. In this work, dithieno[3,2-b:2',3'-d]pyrrole (DTP) is applied as an alternative donor unit in a TADF emitter for the first time. In combination with isophthalonitrile (IPN), the 4CzIPN analogue termed 4DTPIPN is obtained. The strong electron donating nature of the DTP moiety gives rise to a red shift of the emission with respect to that of 4CzIPN. We identify that 4DTPIPN has a very stable emission spectrum throughout all solid-state thin film concentrations and host materials. Rather interestingly, this colour stability is obtained via the formation of dimer/aggregate species that are present even at 0.01 wt% concentration. Unfortunately, the higher colour stability is paired with a low photoluminescence quantum yield, making 4DTPIPN unviable for device applications. Nonetheless, this work shows the importance of dimer contributions, even at dilute doping concentrations. This molecule and study provide important understanding of the aggregation behaviour of small-molecule emitters necessary for the successful application of doped and, especially, non-doped OLED architectures.
Notes: Maes, W (corresponding author), Hasselt Univ, Inst Mat Res IMO IMOMEC, Design & Synth Organ Semicond DSOS, Agoralaan 1, B-3590 Diepenbeek, Belgium.; Maes, W (corresponding author), IMEC, IMOMEC Div, Wetenschapspk 1, B-3590 Diepenbeek, Belgium.; Etherington, MK (corresponding author), Northumbria Univ, Dept Math Phys & Elect Engn, Ellison Pl, Newcastle Upon Tyne NE1 8ST, Tyne & Wear, England.; Etherington, MK (corresponding author), Univ Durham, Dept Phys, OEM Grp, South Rd, Durham DH1 3LE, England.
marc.k.etherington@northumbria.ac.uk; wouter.maes@uhasselt.be
Document URI: http://hdl.handle.net/1942/37200
ISSN: 2050-7526
e-ISSN: 2050-7534
DOI: 10.1039/d1tc04913e
ISI #: WOS:000773109800001
Rights: Open Access Article. Published on 25 March 2022. Downloaded on 4/13/2022 3:06:50 PM. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Category: A1
Type: Journal Contribution
Validations: ecoom 2023
Appears in Collections:Research publications

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