Ehsan Ullah Rashid is a PhD student at Kaunas University of Technology (KTU). He has lead co-authored a groundbreaking study that could significantly transform both organic light-emitting diode (OLED) technology and explosives detection. The research focuses on donor-donor exciplex-forming interfaces and was published in the journal ACS Applied Electronic Materials, bearing the DOI: 10.1021/acsaelm.5c00123. This pioneering research brings important attention to aggregation-enhanced emission. It could significantly increase OLED efficiency and sensitivity to hazardous materials such as picric acid.
Rashid joined forces with other researchers to achieve a scientific breakthrough. He is continuing his work with Monika Čekavičiūtė, a KTU scientist and co-inventor, and Juozas Gražulevičius, a professor at KTU’s Faculty of Chemical Technology. What they achieved together goes against all fundamental rules of light-emitting materials. This breakthrough paves the way for remarkable new applications across military, security and environmental protection realms.
The Concept of Aggregation-Enhanced Emission
This study highlights the prominent role of aggregation at the molecular level, often considered an undesirable characteristic in optoelectronic materials. Rather than being bogged down by these logistical hurdles, the team showed that this aggregation can be a great functional advantage.
“In our study, molecular aggregation, previously seen as a problem, becomes a functional advantage. This fundamentally changes how we approach the use of organic materials in optoelectronics,” – Prof. Gražulevičius
Rashid stressed the significance that their findings hold. He pointed out that the molecules they developed increase luminescence upon packing, the opposite behavior of many organic emitters.
“Unlike many organic emitters whose luminescence decreases when molecules are closely packed, our developed molecules show the opposite effect—their luminescence increases. This phenomenon is known as aggregation-enhanced emission,” – Ehsan Ullah Rashid
The impact of these findings is massive for OLED technology. Rashid explained that their discovery could make OLED production processes cheaper and faster.
“Our discovery can facilitate OLED production, which is crucial both for technological advancement and sustainability,” – Ehsan Ullah Rashid
Novel Applications in Detection Technologies
Their studies point to a compound that goes well beyond existing methods, demonstrating extraordinary sensitivity for nitroaromatic compounds. One of them includes picric acid, which is frequently used in explosives manufacturing. Such sensitivity paves the way for creation of sensors capable of reliably detecting dangerous materials.
It’s pretty gratifying, Dr. Čekavičiūtė added, that their discovery might have a real, practical impact. She proved that materials which can intensely emit light, while suppressing it greatly in the presence of nitroaromatic compounds, can result in dependable sensor technologies.
“Materials that intensively emit light and whose light emission is drastically suppressed in the presence of nitroaromatic compounds enable the creation of sensitive, reliable, and convenient sensors. Such solutions are important not only for military and security applications but also for environmental protection,” – Dr. Monika Čekavičiūtė
In fact, these sensors have far-reaching implications outside of military purposes. They are uniquely qualified to guide historic federal investments to protect public safety and preserve environmental integrity.
Redefining Light-Emitting Materials
This work is groundbreaking in its approach, changing the way the research community thinks about light-emitting materials. Gražulevičius explained that until now, donor-donor interactions were considered virtually unattainable. Beyond its biotechnological implications, their discovery invites a critical re-examination of conventional scientific beliefs regarding molecular interactions.
“Until now, such interactions were considered practically impossible. This discovery challenges the fundamental principles we have used to understand how light-emitting materials work and pushes us to rethink the potential of donor interactions,” – Dr. Juozas Gražulevičius
In addition, their multifunctionality and highly ordered 2D morphology set them apart from conventional organic semiconductors. As Čekavičiūtė explained, this allows them to create two different kinds of complexes—something that is atypical for this group of materials.
“Our materials stand out for their multifunctionality, simple structures, and exceptional photophysical properties. They can form two types of complexes, which is unusual for organic semiconductors,” – Dr. Monika Čekavičiūtė
Rashid, Čekavičiūtė, and Gražulevičius are truly pioneering in their field of OLED technology. Their ongoing collaborative work goes further, too, by developing safer alternatives for explosives and nuclear-contaminated environmental remediation.