Balanced Energy Gaps as a Key Design Rule for Solution‐Phase Organic Room Temperature Phosphorescence

Paredis, Simon; Cardeynaels, Tom; Kuila, Suman; Deckers, Jasper; Van Landeghem, Melissa; Vandewal, Koen; Danos, Andrew; Monkman, Andrew P.; Champagne, Benoît; Maes, Wouter

Abstract

Metal-free organic emitters that display solution-phase room temperature phosphorescence (sRTP) remain exceedingly rare. Here, we investigate the structural and photophysical properties that support sRTP by comparing a recently reported sRTP compound (BTaz-Th-PXZ) to two novel analogous materials, replacing the donor group by either acridine or phenothiazine. The emissive triplet excited state remains fixed in all three cases, while the emissive charge-transfer singlet states (and the calculated paired charge-transfer T2 state) vary with the donor unit. While all three materials show dominant RTP in film, in solution different singlet-triplet and triplet-triplet energy gaps give rise to triplet-triplet annihilation followed by weak sRTP for the new compounds, compared to dominant sRTP throughout for the original PXZ material. Engineering both the sRTP state and higher charge-transfer states therefore emerges as a crucial element in designing emitters capable of sRTP.

Citation

Paredis, S., Cardeynaels, T., Kuila, S., Deckers, J., Van Landeghem, M., Vandewal, K., …Maes, W. (2023). Balanced Energy Gaps as a Key Design Rule for Solution‐Phase Organic Room Temperature Phosphorescence. Chemistry - A European Journal, https://doi.org/10.1002/chem.202301369

• Journal Article Type: Article
• Acceptance Date: May 8, 2023
• Online Publication Date: May 8, 2023
• Publication Date: 2023
• Deposit Date: May 9, 2023
• Publicly Available Date: May 9, 2024
• Journal: Chemistry – A European Journal
• Print ISSN: 0947-6539
• Electronic ISSN: 1521-3765
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.1002/chem.202301369
• Public URL: https://durham-repository.worktribe.com/output/1175576