The 8-hydroxyquinolinium cation as a lead structure for efficient color-tunable ionic small molecule emitting materialsShow others and affiliations
2023 (English)In: Advanced Photonics Research, ISSN 2699-9293, Vol. 4, no 3, article id 2200279Article in journal (Refereed) Published
Abstract [en]
Albeit tris(8-hydroxyquinolinato) aluminum (Alq3) and its derivatives are prominent emitter materials for organic lighting devices, and the optical transitions occur among ligand-centered states, the use of metal-free 8-hydroxyquinoline is impractical as it suffers from strong nonradiative quenching, mainly through fast proton transfer. Herein, it is shown that the problem of rapid proton exchange and vibration quenching of light emission can be overcome not only by complexation, but also by organization of the 8-hydroxyquinolinium cations into a solid rigid network with appropriate counter-anions (here bis(trifluoromethanesulfonyl)imide). The resulting structure is stiffened by secondary bonding interactions such as pi-stacking and hydrogen bonds, which efficiently block rapid proton transfer quenching and reduce vibrational deactivation. Additionally, the optical properties are tuned through methyl substitution from deep blue (455 nm) to blue-green (488 nm). Time-dependent density functional theory (TDFT) calculations reveal the emission to occur from which an unexpectedly long-lived S-1 level, unusual for organic fluorophores. All compounds show comparable, even superior photoluminescence compared to Alq3 and related materials, both as solids and thin films with quantum yields (QYs) up to 40-50%. In addition, all compounds show appreciable thermal stability with decomposition temperatures above 310 °C.
Place, publisher, year, edition, pages
John Wiley & Sons, 2023. Vol. 4, no 3, article id 2200279
Keywords [en]
crystal engineering, organic lighting, photoluminescence, secondary bonding interactions
National Category
Inorganic Chemistry Condensed Matter Physics
Identifiers
URN: urn:nbn:se:umu:diva-218964DOI: 10.1002/adpr.202200279ISI: 000929010500001OAI: oai:DiVA.org:umu-218964DiVA, id: diva2:1824108
Funder
Swedish Foundation for Strategic Research, EM16-0013Swedish Foundation for Strategic Research, 2020-04437Swedish Research Council, 2018-05973Swedish Research Council, 2020-044372024-01-042024-01-042024-01-04Bibliographically approved