According to the FIAN-Inform Scientific Information Agency, staff members of the RAS Institute of Physics named after P. Lebedev (FIAN) in cooperation with scientists from the Moscow Physico-Technical Institute and the Institute of Physics of the National Academy of Ukraine developed a technology to produce new planar (from Latin planus--flat, plane) metalloorganic structures that can be used to manufacture submicron electroluminescent light sources with a controlled emission spectrum.

Conversion to new lighting technologies is a crucial point for modern society. The EU and the USA are already in the process of getting rid of conventional incandescent light bulbs. For example, the EU countries are planning to replace them with energy-saving lamps till 2012. In the USA they will be totally withdrawn from sale till 2014. It is possible that Russia will also prohibit traditional lamps to increase overall energy efficiency. Quite popular luminescent lamps, irrespective of high demand, are difficult to be manufactured and utilized. That's why specialists are in active search for new types of sources based on semiconductor or organic light-emitting diodes, in which the so-called OLED technologies are used (from English Organic Light-Emitting Diode). The Russian and Ukrainian scientists suggest to focus on potentialities of electroluminescent characteristics of metalloorganic structures.

In 2010, there was produced a pilot batch of such low-molecular materials at FIAN. Dmitry Chubich, Cand. Sc. (Phys. & Math.), reported on the completed work: "The planar structure production method is based on thermal spraying of a gold film to a clearance of 30 µm

between two electrodes on a glass support. This process is carried out in ultrahigh vacuum under the pressure of 10 Torn As a result we get a metal film consisting of separate islets. Such structures are already well studied. In our case we studied not a simple metal film, but a composite material-a metal film with an organic layer on top. This organic layer makes it possible to change characteristics of radiation. Varying the organic component, scientists can change the spectrum and thus obtain sub-micron (less than 1 µm) light sources."

The spectrum of luminescent and incandescent lamps is very close to natural sun light we are used to. Light emitted by newly designed lamps is less favorable for a human eye, which prevents the application of a new technology. At the moment, the researchers are trying to find a light source without "superfluous radiation" components in the spectrum and with the basic energy in the visible range. Electroluminescence of structures produced on the basis of the newly developed technology makes it possible to vary significantly the spectrum of a lighting unit, i.e. to create "natural" light lamps.

"As an organic component we used first standard electroluminescent material Alq₃, explained Chubich.--In 1986 it was applied to produce the first in the world organic light-emitting diode. Making sure of operating capabilities of the studied structure, we selected organic complexes of rare earth elements--europium (Eu) and terbium (Tb) (they are easily identified in the spectrum due to their narrow characteristic lines)--and set to study their luminescence origination mechanism."

Finally, the FIAN luminescence department produced planar light-emitting devices on the basis of detached films of gold and Eu and Tb complexes, and discovered the electroluminescence mechanism of the structure under consideration--it turned out that the organic component dominated in it. According to scientists, such structures may be used as submicron light sources with a narrow red and green spectrum of radiation. Terbium-based materials are characterized by almost 100 percent efficiency of photoluminescence. Efficiency of samples studied at the Institute of Physics was registered at the level of about 95 percent, i.e. they emit almost all light they absorb with an insignificant change of wave length (in the best Japanese samples this indicator is a little bit worse), which means that this technology is highly perspective for production of different light sources and displays. In future, organic diodes could be used to improve characteristics of optoelectronic devices and will likely replace existing inorganic light-emitting diodes.

According to the materials of the FIAN-Inform Scientific Information Agency, May 5, 2010

Prepared by Marina KHALIZEVA