4
A molecular "merry-go-round" complex will make OLED screens twice as bright

A molecular "merry-go-round" complex will make OLED screens twice as bright

A RUDN University chemist synthesized fluorescent compounds with "merry-go-round" molecules that can be used to create economical displays with organic LEDs (OLED). The nucleus of these molecules is a triangle of silver or copper atoms, and organic elements are bound to it through phosphorus atoms and are able to rotate around them. This molecular geometry doubled the quantum yield of luminescence to 41 percent. In modern OLED screens, this figure is 20 percent. The article is published in Inorganic Chemistry.

Displays with organic LEDs differ from other modern types of displays, plasma and LCD, in higher brightness, contrast and lower power consumption. However, OLED displays are more expensive. Also, the raw material for their production – conductive polymers – is toxic, and it creates difficulties in production and disposal.

To reduce the cost of OLED displays and get rid of toxic raw materials, it is possible to use fluorescent complex compounds — molecules where small organic fragments surround the central ion of the metal instead of polymers. But so far, it has not been possible to find complexes that would show a clear advantage in brightness and efficiency over polymers. Sufficiently effective compounds based on iridium or platinum were very expensive, and cheaper complexes with transition metal ions were not effective enough.

RUDN University chemist Alexander Smolyakov, an employee of the Scientific Center "Cluster of target synthesis of natural compounds", found compounds that would make OLED displays much brighter and more economical than polymer ones. The centers of these complexes were not platinum or iridium, but cheaper copper and silver, which also proved to be more effective and less toxic compared to polymers.

The researcher synthesized a molecule with not one but three ions of monovalent copper or silver in the center. To make this structure of three metal ions stronger, the chemist stabilized it using derivatives of pyrazole — aromatic molecules with two nitrogen atoms in the cycle, and used organophosphorus molecules as ligands (molecules — electron donors surrounding an ion). In this case, the ions of monovalent copper and silver form a three-center nucleus in the form of a triangle, and ligands join the nucleus through phosphorus atoms and remain quite mobile.

At room temperature, the energy of thermal oscillations is sufficient to break the bond between phosphorus and metal for a short time. However, there are two phosphorus atoms in a molecule, and there are three metal atoms. So one of the metal atoms always is without a pair and if there is a single phosphorus atom, the metal atom attracts it immediately. That is, the ligand "jumps" to the neighboring ion in the three-center nucleus and forms a bond that can soon be destroyed again due to thermal fluctuations.

The molecule thus turns into a kind of molecular "merry-go-round". This configuration makes stable complexes with nuclei of silver ions, and complexes with nuclei of monovalent copper — compounds do not decay immediately after synthesis, like many other structures of this type.

Chemists have found that such "merry-go-round" structure of complex compounds leads to the emergence of two energy states, the transition between which can lead to luminescence. In the case of copper, this structure has a significant quantum yield – that is, the ratio of the number of absorbed and emitted photons is 41 percent. The organic polymers that are used in OLED displays today provide a quantum yield twice as low: about 20 percent.

Scientists think that three-center copper "merry-go-round" complexes are promising for the future of OLED technology.

The article in Inorganic Chemistry

30 Jan 2018
The conference on international arbitration, where law students from European universities simulate court proceedings and alternately defend the interests of the respondent and the orator.
1312
Visiting Professors View all
03 Nov 2017
Michele Pagano is a graduate of the University of Pisa, a leading scientist, the author of more than 200 publications in international journals, and a participant in many international research projects
3158
Similar newsletter View all
16 Oct
Green Diplomacy Center opened in RUDN

A Center for Green Diplomacy was created based on the RUDN Institute of Environmental Engineering. Among the goals is the integration of the results of scientific and practical activities into the development of international relations in the environmental sphere. The center's specialists will also accompany the corporate sector in solving various environmental problems.

131
19 Apr
A huge pizza and a jug of water, why should 5G networks be sliced? The winners of RUDN science competition explain

RUDN summarized the results of the scientific competition "Project Start: work of the science club ". Students of the Faculty of Physics, Mathematics and Natural Sciences have created a project for a managed queuing system using a neural network to redistribute resources between 5G segments. How to increase flexibility, make the network fast and inexpensive and reach more users — tell Gebrial Ibram Esam Zekri ("Fundamental Computer Science and Information Technology", Master's degree, II course) and Ksenia Leontieva ("Applied Mathematics and Computer Science", Master's degree, I course).

184
19 Apr
Lyricists and physicists are now on equal terms: the first humanitarian laboratory opened in RUDN

What is your first association with the word “laboratory”? Flasks and beakers? Microscopes and centrifuges? Yes, many of us would answer the same way.

231
Similar newsletter View all