Delayed Fluorescence by Triplet–Triplet Annihilation from Columnar Liquid Crystal Films

Gomes Franca, Larissa; dos Santos, Paloma L.; Pander, Piotr; Cabral, Marília G.B.; Cristiano, Rodrigo; Cazati, Thiago; Monkman, Andrew P.; Bock, Harald; Eccher, Juliana

doi:10.1021/acsaelm.2c00432

Delayed Fluorescence by Triplet–Triplet Annihilation from Columnar Liquid Crystal Films

Gomes Franca, Larissa; dos Santos, Paloma L.; Pander, Piotr; Cabral, Marília G.B.; Cristiano, Rodrigo; Cazati, Thiago; Monkman, Andrew P.; Bock, Harald; Eccher, Juliana

Authors

Larissa Franca larissa.gomes-franca@durham.ac.uk
PGR Student Doctor of Philosophy

Dr Paloma Lays dos Santos paloma.l.dos-santos@durham.ac.uk
Academic Visitor

Piotr Pander piotr.h.pander@durham.ac.uk
Academic Visitor

Marília G.B. Cabral

Rodrigo Cristiano

Thiago Cazati

Professor Andrew Monkman a.p.monkman@durham.ac.uk
Professor

Harald Bock

Juliana Eccher

Abstract

Delayed fluorescence (DF) by triplet–triplet annihilation (TTA) is observed in solutions of a benzoperylene-imidoester mesogen that shows a hexagonal columnar mesophase at room temperature in the neat state. A similar benzoperylene-imide with a slightly smaller HOMO–LUMO gap, that also is hexagonal columnar liquid crystalline at room temperature, does not show DF in solution, and mixtures of the two mesogens show no DF in solution either, because of collisional quenching of the excited triplet states on the imidoester by the imide. In contrast, DF by TTA from the imide but not from the imidoester is observed in condensed films of such mixtures, even though neat films of either single material are not displaying DF. In contrast to the DF from the monomeric imidoester in solution, DF of the imide occurs from dimeric aggregates in the blend films, assisted by the imidoester. Thus, the close contact of intimately stacked molecules of the two different species in the columnar mesophase leads to a unique mesophase-assisted aggregate DF. This constitutes the first observation of DF by TTA from the columnar liquid crystalline state. If the imide is dispersed in films of polybromostyrene, which provides an external heavy-atom effect facilitating triplet formation, DF is also observed. Organic light-emitting diodes (OLEDs) devices incorporating these liquid crystal molecules demonstrated high external quantum efficiency (EQE). On the basis of the literature and to the best of our knowledge, the EQE reported is the highest among nondoped solution-processed OLED devices using a columnar liquid crystal molecule as the emitting layer.

Citation

Gomes Franca, L., dos Santos, P. L., Pander, P., Cabral, M. G., Cristiano, R., Cazati, T., …Eccher, J. (2022). Delayed Fluorescence by Triplet–Triplet Annihilation from Columnar Liquid Crystal Films. ACS Applied Electronic Materials, 4(7), https://doi.org/10.1021/acsaelm.2c00432

Journal Article Type	Article
Acceptance Date	Jun 13, 2022
Online Publication Date	Jun 27, 2022
Publication Date	2022
Deposit Date	Aug 1, 2022
Publicly Available Date	Aug 1, 2022
Journal	ACS Applied Electronic Materials
Print ISSN	2637-6113
Electronic ISSN	2637-6113
Publisher	American Chemical Society
Peer Reviewed	Peer Reviewed
Volume	4
Issue	7
DOI	https://doi.org/10.1021/acsaelm.2c00432

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