A bright future in eco-friendly light devices, just add dendrimers,
cellulose, and graphene

Date:
July 7, 2023
Source:
Kyushu University
Summary:
Researchers have developed a light-emitting electrochemical
cell using dendrimers, a material gaining popularity in
the industry. Moreover, the team found that using biomass
derived cellulose acetate as the electrolyte retains the cell's
long-life span. Combined with a graphene electrode, the cell has
the potential to light the way for a future of eco-friendly and
flexible light-emitting devices.


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FULL STORY ==========================================================================
In research that could lead to a new age in illumination, researchers
from Japan and Germany have developed an eco-friendly light-emitting electrochemical cells using new molecules called dendrimers combined
with biomass derived electrolytes and graphene-based electrodes. Their
findings were published in the journal Advanced Functional Materials.

Electroluminescence is the phenomenon where a material emits light
in response to a passing electric current. Everything from the screen
you're using to read this sentence to the lasers used in cutting edge scientific research are results of the electroluminescence of different materials. Due to its ubiquity and necessity in the modern age, it is
only natural that extensive resources go into research and development
to make this technology better.

"One such example of an emerging technology is 'light-emitting
electrochemical cells' or LECs," explains Associate Professor Ken
Albrechtfrom Kyushu University's Institute for Materials Chemistry and Engineering and one of the leads of the study. "They have been attracting attention because of their cost advantage over organic light emitting
diodes, or OLEDs. Another reason for LECs popularity is their simplified structure." OLED devices generally require the carful layering of
multiple organic films, making it tricky and costly to manufacture. LECs
on the other hand can be made with a single layer of organic film mixed
with light-emitting materials and an electrolyte. The electrode that
connects it all together can even be made from inexpensive materials
unlike the rare or heavy metals used in OLEDs. Moreover, LECs have lower driving voltage, meaning they consume less energy.

"Our research teams have been exploring new organic materials that can be
used in LECs. One such candidate are dendrimers," explains Prof. Rube'n
D. Costa of the Technical University of Munich, who led the research
team in Germany.

"These are branched symmetric polymeric molecules whose unique structure
has led to their utility in everything from medicine to sensors, and
now in optics." Building upon their past work on developing dendrimers,
the research team began modifying their materials for LECs.

"The dendrimer we developed initially had hydrophobic, or water repelling, molecular groups. By replacing this with hydrophilic, or water liking,
groups we found that the lifetime of the LEC device could be extended
to over 1000 hours, more than 10-fold from the original," explains
Albrecht. "What makes it even better is that thanks to our collaboration
with Dr Costa's team the device is very eco-friendly." For years,
Costa's team in Germany had been working on developing cheaper and more environmentally friendly materials in light-emitting devices. One material
they have been experimenting with is cellulose acetate, a common organic compound used in everything from clothing fibers and eyeglass frames.

"We used biomass derived cellulose acetate as the electrolyte in our
new LEC device, and confirmed that it has the same long-life span,"
continues Costa.

"Moreover, we also found that graphene can be used as an electrode
as well.

This is a vital step toward making flexible light-emitting devices using environmentally friendly materials." The team explains that while their
work is promising more research is necessary before the devices can be
made to market.

"The device we made here only illuminates in yellow, so we need to develop
it to illuminate in the three primary light colors: blue, green, and red.

Luminescence efficiency, how bright the light is, also needs work,"
concludes Albrecht. "Though thanks to our international collaboration,
the future looks bright."
* RELATED_TOPICS
o Matter_&_Energy
# Optics # Graphene # Chemistry # Materials_Science
# Inorganic_Chemistry # Civil_Engineering #
Engineering_and_Construction # Organic_Chemistry
* RELATED_TERMS
o Solar_cell o Electroluminescence o Xenon o Photography o
Gallium o Solar_power o Optics o Electric_power

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========================================================================== Journal Reference:
1. Luca M. Cavinato, Keiko Yamaoka, Sophia Lipinski, Vladimir Calvi,
Dominique Wehenkel, Richard van Rijn, Ken Albrecht, Rube'n D. Costa.

Dendri‐LEC Family: Establishing the Bright Future for
Dendrimer Emitters in Traditional and Graphene‐Based
Light‐Emitting Electrochemical Cells. Advanced Functional
Materials, 2023; DOI: 10.1002/ adfm.202302483 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230707111656.htm

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