(2023/06/29)

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A bright future in eco-friendly light devices, just add dendrimers, cellulose, andgraphene
Researchers from Japan and Germany have developed a new eco-friendly, and long-lasting
light-emitting electrochemical cell using dendrimers combined with biomass derived cellulose
acetate as the electrolyte and a graphene electrode
Fukuoka, Japan—In research that could lead to a new age in illumination, researchers fromJapan and Germany have developed an eco-friendly light-emitting electrochemical cells using
new molecules called dendrimers combined with biomass derived electrolytes and graphenebased 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 differentmaterials. 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' orLECs," explains Associate Professor Ken Albrecht from Kyushu University's Institute forMaterials 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, orOLEDs. Another reason for LECs popularity is their simplified structure."OLED devices generally require the carful layering of multiple organic films, making it tricky andcostly 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 inOLEDs. 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. Rubén D. Costa of the Technical
University of Munich, who led the research team in Germany. "These are branched symmetricpolymeric molecules whose unique structure has led to their utility in everything frommedicine 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 theLEC 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 moreenvironmentally friendly materials in light-emitting devices. One material they have been
experimenting with is cellulose acetate, a common organic compound used in everythingfrom clothing fibers and eyeglass frames.
"We used biomass derived cellulose acetate as the electrolyte in our new LEC device, andconfirmed that it has the same long-life span," continues Costa. "Moreover, we also foundthat 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 thedevices 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 thelight is, also needs work," concludes Albrecht. "Though thanks to our international
collaboration, the future looks bright."###For more information about this research, see "Dendri-LEC Family: Establishing the Bright
Future for Dendrimer Emitters in Traditional and Graphene-Based Light-Emitting
Electrochemical Cells," Luca M. Cavinato, Keiko Yamaoka, Sophia Lipinski, Vladimir Calvi,
Dominique Wehenkel, Richard van Rijn, Ken Albrecht, and Rubén D. Costa Advanced
Functional Materials, https://doi.org/10.1002/adfm.202302483
About Kyushu University
Kyushu University is one of Japan's leading research-oriented institutes of higher education
since its founding in 1911. Home to around 19,000 students and 8,000 faculty and staff,
Kyushu U's world-class research centers cover a wide range of study areas and research
fields, from the humanities and arts to engineering and medical sciences. Its multiple
campuses—including one of the largest in Japan—are located around Fukuoka City, a coastal
metropolis on the southwestern Japanese island of Kyushu that is frequently ranked among
the world's most livable cities and historically known as Japan's gateway to Asia. Through its
Vision 2030, Kyushu U will 'Drive Social Change with Integrative Knowledge.' Its synergistic
application of knowledge will encompass all of academia and solve issues in society while
innovating new systems for a better future.

Fig. 1. New dendrimers and longer half-life.
Second-generation dendrimers with tert-butyl(left) and methoxy groups (right) applied tolight-emitting electrochemical cells (LEC). The
lifetime of LEC devices using dendrimers withhydrophilic methoxy groups (right) is more than
10 times longer than that of hydrophobic
dendrimers. (Kyushu University/Albrecht Lab)[Contact]
Albrecht Ken, Associate Professor
Department of Integrated Materials, Institute for Materials Chemistry and Engineering
Tel: +81-92-583-7815
E-mail: ablrecht@cm.kyushu-u.ac.jp
Website: https://www.alken-lab.com/