Organic dyes with persistent delayed fluorescence and ultralong phosphorescence
A team of researchers from Lithuania has developed organic dyes
showing a particularly long afterglow after being excited by light.
Doping a polymer with newly synthesized diboraanthracene dyes resulted
in an intense red or blue–green dual afterglow, which was composed of
persistent thermally activated delayed fluorescence and long
phosphorescence at room temperature, the team reports in the journal Angewandte Chemie.
Such organic materials can find important optoelectronic applications,
such as in data encryption, information recording, and sensors.
© Wiley-VCH, re-use with credit to 'Angewandte Chemie' and a link to the original article.
“When you try to develop materials with a more efficient
phosphorescence, the problem is that a more intensive phosphorescence
often results in the decrease of phosphorescence lifetime and vice
versa,” says Justina Jovaišaitė from Vilnius University (Lithuania), the
corresponding author of the study. To overcome this problem, the team
developed diboraanthracene dyes, for which the efficiency of
long-lasting phosphorescence was supplemented by the efficiency of
persistent thermally activated delayed fluorescence.
To achieve the desired dual afterglow, the team modified the
diboraanthracene scaffold by synthetic methods. Diboraanthracene
compounds have the basic aromatic structure of the organic chemical
anthracene but contain two boron atoms. Synthetic modification not only
lead to a more intense afterglow than in purely phosphorescing
materials, but it also allowed the researchers to create organic dyes
with different afterglow colors, which were tunable. “Upon cooling, the
afterglow color either shifted from red to green or from green to blue.
This can be of extreme importance for development of temperature
sensors,” Jovaišaitė says.
The newly developed organic dyes could be used in data recording and
information encryption. To demonstrate this, the researchers prepared
transparent layers coated by the studied organic compounds. They
irradiated the samples with intense laser light to write information,
which could be read when the entire layer was exposed to less intense UV
light.
The researchers hope that, through more in-depth investigation of the
photophysical properties of their system, they will be able to optimize
and control these afterglow properties further. They plan to increase
duration, efficiency, and tunability of the afterglow. “Polymer-based
organic afterglow materials are desirable because of their flexibility,
transparency, and suitability for large-scale production,” Jovaišaitė
says.
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About the Author
Justina Jovaišaitė
is a Junior Research Fellow in the Organic Optoelectronics group led by
Saulius Antanas Juršėnas at the Institute of Photonics and
Nanotechnology at Vilnius University (Lithuania). She investigates
photophysical properties of organic molecules with a special focus on
electron donor–acceptor organic compounds with intramolecular
charge-transfer character. The research interests of the Organic
Optoelectronics group mostly cover the investigation of excitation
dynamics in various organic materials that are used for sensing,
light-upconversion, or development of OLED emitters.