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

International scientific cooperation View all
03 Nov 2017
The main goal of the RUDN University and UNISDR Office for Northeast Asia and Global Education and Training Institute for Disaster Risk Reduction at Incheon (UNISDR ONEA-GETI) cooperation is to obtain knowledge about disaster risk reduction and international experience in this area for creating training courses for basic and additional professional education in RUDN
1014
Scientific Conferences View all
03 Nov 2017
RUDN University organized the first 5G Summit R&D Russia on June 19 - 20, 2017
1408
Similar newsletter View all
31 Mar
RUDN University awards for specific areas of science and technology based on the results of 2021

Every year, RUDN University selects the best of the best in the field of science and innovation and encourages with a special reward. Since 2009, the Academic Council of the University has been awarding one reward in natural and technical sciences and the other one in social and humanitarian sciences. Both individual researchers and groups of authors can become laureates.

72
31 Mar
International Day of Women and Girls in Science: women scientists of the RUDN talk about their path to science

“Science is the basis of all progress that facilitates the life of mankind and reduces its suffering,” — Marie Sklodowska—Curie. A symbol of a woman’s success in science. The first scientist in the world — twice winner of the Nobel Prize.

315
31 Mar
RUDN University Mathematicians Create a Model for Queue Organizing with Self-Sustained Servers

RUDN University mathematicians proposed a model for optimizing the operation of queuing systems (from computer networks to stores). Unlike analogues, the servers in it are self-sustained. They can determine when to start and stop working themselves. Such a model can be useful, for example, for online taxi services and other systems where workers choose their own operating hours.

80
Similar newsletter View all