Metal-free organic 3-bromo-2-thienyl diketones exhibit fast and highly efficient room-temperature phosphorescence with high color purity under various conditions, according to new research led by Osaka University chemists.
An artist’s impression of fast phosphorescence: the blue light rays come into the molecule to generate bold yellow pillars, representing the acceleration of phosphorescence through the mixing of singlet states. Image credit: YAP Co Ltd.
“Phosphorescence is a valuable optical function used in applications such as OLEDs and cancer diagnostics,” said Osaka University chemist Yosuke Tani and colleagues.
“Until now, achieving high-efficiency phosphorescence without using rare metals such as iridium and platinum has been a significant challenge.”
“Phosphorescence, which occurs when a molecule transitions from a high-energy state to a low-energy state, often competes with non-radiative processes where the molecule loses energy as heat,” they added.
“This competition can lead to slow phosphorescence and lower efficiency.”
“While previous research indicated that incorporating certain structural elements into organic molecules could speed up phosphorescence, these efforts have not matched the speed and efficiency of rare metal-based materials.”
“Our breakthrough with thienyl diketones represents a significant advancement in the field.”
Dr. Tani and co-authors were able to observe efficient narrowband room-temperature phosphorescence from 3-bromo-2-thienyl diketones in solutions, amorphous polymer matrices, and crystalline solids.
“We discovered theses molecule by chance and initially did not understand why they demonstrated such superior performance,” Dr. Tani said.
“However, as our research progressed, we began to connect the pieces and deepen our understanding.”
“Our research has led to a clearer understanding of the mechanism behind the molecules’ performance than any previous organic phosphorescent material.”
“Nonetheless, we believe there is still much to explore, and we are excited about its potential applications.”
“This research provides new design guidelines for developing organic phosphorescent materials that do not rely on rare metals, offering the potential to surpass and replace these materials in various applications,” the authors concluded.
“The findings promise significant advancements in the fields of OLEDs, lighting, and medical diagnostics, among others.”
The discovery is reported in a paper in the journal Chemical Science.
_____
Yosuke Tani et al. Fast, efficient, narrowband room-temperature phosphorescence from metal-free 1,2-diketones: rational design and the mechanism. Chemical Science, published online June 3, 2024; doi: 10.1039/D4SC02841D
