| 1. |
- Hultmark, Sandra, 1994, et al.
(författare)
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Vitrification of octonary perylene mixtures with ultralow fragility
- 2021
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:29
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Tidskriftsartikel (refereegranskat)abstract
- Strong glass formers with a low fragility are highly sought-after because of the technological importance of vitrification. In the case of organic molecules and polymers, the lowest fragility values have been reported for single-component materials. Here, we establish that mixing of organic molecules can result in a marked reduction in fragility. Individual bay-substituted perylene derivatives display a high fragility of more than 70. Instead, slowly cooled perylene mixtures with more than three components undergo a liquid-liquid transition and turn into a strong glass former. Octonary perylene mixtures display a fragility of 13 +/- 2, which not only is a record low value for organic molecules but also lies below values reported for the strongest known inorganic glass formers. Our work opens an avenue for the design of ultrastrong organic glass formers, which can be anticipated to find use in pharmaceutical science and organic electronics.
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| 2. |
- Kushwaha, Khushbu, et al.
(författare)
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A Record Chromophore Density in High-Entropy Liquids of Two Low-Melting Perylenes: A New Strategy for Liquid Chromophores
- 2019
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Ingår i: Advanced Science. - : Wiley. - 2198-3844. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- Liquid chromophores constitute a rare but intriguing class of molecules that are in high demand for the design of luminescent inks, liquid semiconductors, and solar energy storage materials. The most common way to achieve liquid chromophores involves the introduction of long alkyl chains, which, however, significantly reduces the chromophore density. Here, strategy is presented that allows for the preparation of liquid chromophores with a minimal increase in molecular weight, using the important class of perylenes as an example. Two synergistic effects are harnessed: (1) the judicious positioning of short alkyl substituents, and (2) equimolar mixing, which in unison results in a liquid material. A series of 1-alkyl perylene derivatives is synthesized and it is found that short ethyl or butyl chains reduce the melting temperature from 278 degrees C to as little as 70 degrees C. Then, two low-melting derivatives are mixed, which results in materials that do not crystallize due to the increased configurational entropy of the system. As a result, liquid chromophores with the lowest reported molecular weight increase compared to the neat chromophore are obtained. The mixing strategy is readily applicable to other pi-conjugated systems and, hence, promises to yield a wide range of low molecular weight liquid chromophores.
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| 3. |
- Mony, Jürgen, et al.
(författare)
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Angle-Independent Polariton Emission Lifetime Shown by Perylene Hybridized to the Vacuum Field Inside a Fabry-Perot Cavity
- 2018
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 122:43, s. 24917-24923
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Tidskriftsartikel (refereegranskat)abstract
- The formation of hybrid light-matter states in optical structures, manifested as a Rabi splitting of the eigenenergies of a coupled system, is one of the key effects in quantum optics. The hybrid states (exciton polaritons) have unique chemical and physical properties and can be viewed as a linear combination of light and matter. The optical properties of the exciton polaritons are dispersive by nature, a property inherited from the photonic contribution to the polariton. On the other hand, the polariton lifetime in organic molecular systems has recently been highly debated. The photonic contribution to the polariton would suggest a lifetime on the femtosecond time scale, much shorter than experimentally observed. Here, we increase the insights of light-mater states by showing that the polariton emission lifetime is nondispersive. A perylene derivative was strongly coupled to the vacuum field by incorporating the molecule into a Fabry-Perot cavity. The polariton emission from the cavity was shown to be dispersive, but the emission lifetime was nondispersive and on the time scale of the bare exciton. The results were rationalized by the exciton reservoir model, giving experimental evidence to currently used theories, thus improving our understanding of strong coupling phenomena in molecules.
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| 4. |
- Mony, Jürgen, et al.
(författare)
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Interplay between Polaritonic and Molecular Trap States
- 2022
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:18, s. 7965-7972
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Tidskriftsartikel (refereegranskat)abstract
- Strong exciton-photon coupling exhibits the possibility to modify the photophysical properties of organic molecules. This is due to the introduction of hybrid light-matter states, called polaritons, which have unique physical and optical properties. Those strongly coupled systems provide altered excited-state dynamics in comparison to the bare molecule case. In this study, we investigate the interplay between polaritonic and molecular trap states, such as excimers. The molecules used in this study show either prompt or delayed emission from trap states. For both cases, a dear dependency on the exciton-photon energy tuning was observed. Polaritonic emission gradually increased with a concurrent removal of aggregation-induced emission when the systems were tuned toward lower energies. For prompt emission, it is not dear whether the experimental results are best explained by a predominant relaxation toward the lower polariton after excitation or by a direct excimer to polariton transition. However, for the delayed emission case, trap states are formed on the initially formed triplet manifold, making it evident that an excimer-to-polariton transition has occurred. These results unveil the possibility to control the trap state population by creating a strongly coupled system, which may form a mitigation strategy to counteract detrimental trap states in photonic applications.
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| 5. |
- Ye, Chen, et al.
(författare)
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Optimizing photon upconversion by decoupling excimer formation and triplet triplet annihilation
- 2020
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 22:3, s. 1715-1720
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Tidskriftsartikel (refereegranskat)abstract
- Perylene is a promising annihilator candidate for triplet-triplet annihilation photon upconversion, which has been successfully used in solar cells and in photocatalysis. Perylene can, however, form excimers, reducing the energy conversion efficiency and hindering further development of TTA-UC systems. Alkyl substitution of perylene can suppress excimer formation, but decelerate triplet energy transfer and triplet-triplet annihilation at the same time. Our results show that mono-substitution with small alkyl groups selectively blocks excimer formation without severly compromising the TTA-UC efficiency. The experimental results are complemented by DFT calculations, which demonstrate that excimer formation is suppressed by steric repulsion. The results demonstrate how the chemical structure can be modified to block unwanted intermolecular excited state relaxation pathways with minimal effect on the preferred ones.
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