Steam or liquid?
Organic Optoelectronics – a rapidly developing area of research that promises to make available light, flexible and transparent electronic devices of the new generation, such as organic svetotranzistory and organic lasers pumped by electric shock – cherished dream any laser scientists. This is a very promising field: if only because of its accessibility organic semiconductors, in principle, could even oust silicon with its electronic throne.
Until now, it was believed that organic semiconductor crystals grown by crystallization from the vapor phase, is far preferable to those that are grown from solutions because of the couple can get cleaner, more free impurities structure. A group of physicists from the Moscow State University, led by Professor Dmitri Parashchuk refers to those researchers who do not share this opinion and mortar rely on growing for several reasons, particularly because of the more simple and cheap technologies applied in this case. As it turned out, the researchers did not knowingly favored solutions:
scientists were able to grow organic semiconductor crystals with the ability to record high svetoizluchatelnoy that promise a revolution in organic optoelectronics.
Moreover, physicists have made a double breakthrough, using crystal growth is much simpler and cheaper technology is still considered hopeless. The results of their work, scientists published in the latest issue of the journal Applied Materials and Interfaces.
The quantum yield exceeded expectations
As the base polymer for the research they have chosen the so-called thiophene-phenylene oligomers. The desired molecules were synthesized by chemists for them – colleagues from Moscow State University and the Institute of Synthetic Polymeric Materials RAS. Because these molecules were the MSU crystals grown from solution, here measured by their luminescent and electrical properties.
The main result of this study were stunning, “mortar” Crystal Light is stronger than their counterparts obtained by other researchers of a couple.
Their quantum yield (ie the number of emitted photons with respect to the merger) reached 60%, whereas the same crystals, but “a couple” were given no more than 38%.
This is a striking difference in the luminosity of Physics explain in particular the fact that, perhaps, with mortar growing crystals are suppressed some internal non-radiative relaxation channels, takes over the part of the absorbed energy, but, apparently, it is not the only explanation.
«We have We find the reasons for such a high quantum yield, but are not yet ready to publish them. This is a matter of our future studies, “- said Professor Parashchuk.
Flexible screens and lasers
The luminosity was not the only advantage of” mortar “techniques. In one of his past research group Parashchuk found that crystals can be grown on the surface of the solution instead of solid support – due to surface tension forces. And these crystals are the same quality as the crystals’ of the couple ».
“We have shown that a variety of ways to grow crystals on the surface of the liquid, – says Professor Parashchuk. – Roughly speaking, all of these methods reduced to the fact that placing a solution with molecules in some vessel and began to cool it, we will, under certain conditions, allows molecules to be deposited on the surface, at the “liquid – air».
Since this surface is almost perfect, the crystals grow on it are very good, quality and electronic characteristics are not inferior grown out of steam.
Furthermore, the surface of the crystal turns out very smooth, with angstrom rough, which allows you to create on their basis of field-effect transistors, which is an indispensable ».
The physicist emphasizes that the applicability of their crystals svetotranzistorah, and hence in organic optoelectronics, – it is only an assumption, the validity of which still need to prove. However, if the crystals will be able to put into practice, they will make the production of flexible and transparent electronic devices much cheaper. The same can be said about the availability of this laser-based electrically pumped, that is laser controlled by an electric current. “Get these lasers that can” light “, a film by simply connecting to the source, people dream for a long time, but as yet they have not received – said Parashchuk. – We hope that with the help of organic crystals, we can bring this goal. The combination of good conductivity and high efficiency of light emission allows us to hope that it is on such crystals will be made the first electrically pumped laser ».
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