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Goll FD, Schelhorn A, Litvinas D, Tenopala-Carmona F, Kazak L, Jelezko F, Lambert C, Gather MC, Kuehne AJC, Ziener U. Revealing the Origin of Fast Delayed Fluorescence in a Donor Functionalized Bisterpyridine. Chemistry 2024; 30:e202303067. [PMID: 37902606 DOI: 10.1002/chem.202303067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 10/27/2023] [Accepted: 10/30/2023] [Indexed: 10/31/2023]
Abstract
A new carbazole-substituted bisterpyridine with pronounced delayed fluorescence is presented. While the molecular donor-acceptor-donor design suggests the origin of this to be thermally activated delayed fluorescence (TADF), results from various photophysical characterizations, OLED characteristics, temperature-dependent NMR spectroscopy, and DFT calculations all point against the involvement of triplet states. The molecule exhibits blue emission at about 440 nm with two or more fast decay channels in the lower nanosecond range in both solution and thin films. The delayed emission is proposed to be caused by rotational vibrational modes. We suggest that these results are generally applicable, especially for more complex molecules, and should be considered as alternative or competitive emissive relaxation pathways in the field of organic light emitting materials.
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Affiliation(s)
- Felix D Goll
- Institute of Organic Chemistry III -, Macromolecular Chemistry and Organic Materials, Ulm University, 89081, Ulm, Germany
| | - Andreas Schelhorn
- Institute of Organic Chemistry III -, Macromolecular Chemistry and Organic Materials, Ulm University, 89081, Ulm, Germany
| | - Džiugas Litvinas
- Humboldt Centre for Nano- and Biophotonics, Department of Chemistry, University of Cologne, Greinstraße 4-6, 50939, Köln, Germany
| | - Francisco Tenopala-Carmona
- Humboldt Centre for Nano- and Biophotonics, Department of Chemistry, University of Cologne, Greinstraße 4-6, 50939, Köln, Germany
| | - Lev Kazak
- Institute for Quantum Optics, Ulm University, 89081, Ulm, Germany
| | - Fedor Jelezko
- Institute for Quantum Optics, Ulm University, 89081, Ulm, Germany
| | - Christoph Lambert
- Institut für Organische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Malte C Gather
- Humboldt Centre for Nano- and Biophotonics, Department of Chemistry, University of Cologne, Greinstraße 4-6, 50939, Köln, Germany
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, KY16 9SS, St Andrews, Fife, UK
| | - Alexander J C Kuehne
- Institute of Organic Chemistry III -, Macromolecular Chemistry and Organic Materials, Ulm University, 89081, Ulm, Germany
| | - Ulrich Ziener
- Institute of Organic Chemistry III -, Macromolecular Chemistry and Organic Materials, Ulm University, 89081, Ulm, Germany
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Ščajev P, Litvinas D, Kreiza G, Stanionytė S, Malinauskas T, Tomašiūnas R, Juršėnas S. Highly efficient nanocrystalline Cs xMA 1-xPbBr x perovskite layers for white light generation. Nanotechnology 2019; 30:345702. [PMID: 30995629 DOI: 10.1088/1361-6528/ab1a69] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Perovskite light converting layers optimization for cost-efficient white light emitting diodes (LED) was demonstrated. High excitation independent internal quantum efficiency (IQE) of 80% and weakly excitation dependent PL spectra suitable for white light generation were obtained in the mixed cation CsxMA1-xPbBr3 perovskite nanocrystal layers with optimal x = 0.3 being determined by effective surface passivation and phase mixing as revealed by x-ray diffraction. Enhancement of the PL homogeneity and the external quantum efficiency (EQE) were secured when using 2,2',2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole (TPBi) additive in the layer preparation process. Excitation dependent PL intensity, decay time, and IQE revealed that the high emission efficiency of the layers originates from a dominant radiative localized exciton recombination (130 ns) weakly influenced by the nonradiative free carrier recombination (750 ns). Warm and cool white LEDs with correlated color temperature 3000 K and 5600 K, and color rendering index 82 and 74, respectively, were realized by using the optimized perovskite layers, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) red emitter and a blue LED.
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Affiliation(s)
- Patrik Ščajev
- Institute of Photonics and Nanotechnology, Vilnius University, Sauletekio ave. 3, LT 10257, Vilnius, Lithuania
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