Perylene is a common annihilator in triplet–triplet annihilation photon upconversion schemes. It has however a tendency for excimer formation, which can be reduced by mono-alkylation without severely compromising the TTA-UC efficiency.
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–Pérot 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.
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 °C to as little as 70 °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 π‐conjugated systems and, hence, promises to yield a wide range of low molecular weight liquid chromophores.
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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