JUL 20, 2016 7:26 AM PDT

New Molecule Advances Field of Organic Electronics

WRITTEN BY: Carmen Leitch
Organic electronics was established as a field of study relatively recently; much of the early work was simply establishing data on conductive organic materials. The first organic diode was made in 1987 and since then the field has grown considerably and includes organic light emitting devices and field-effect transistors. If your eyes are already starting to glaze over, check out this video below from Veritaseum to get some background.
While much of the current work aims to create electronics using organic materials, it’s still not comparable to standard electronics in terms of performance or durability. If those limitations can be overcome, organic materials present many advantages such as low weight, flexibility, transparency, and crucially, plastic electronics are far cheaper than the current silicon stuff. The main uses for organic electronics include solar cells, a technology severely impeded by high costs, which restrict it from efficient coverage of big areas.

Scientists from the Moscow State University (MSU) in collaboration with colleagues from Germany have found that a derivative of [3]-radialene, can be used to create organic semiconductors. Publishing in Advanced Materials, Dmitry Ivanov, the Head of the Laboratory of Materials Engineering at the Department of Fundamental Physics and Chemical Engineering at MSU, believes that the achievement will greatly contribute to the development of organic electronics and, in particular, to fabrication of organic light emitting diodes and new classes of organic solar cells.
The energy levels of the studied systems and a synchrotron X-ray diffractogram measured on a thin film of an organic semiconductor doped with a derivative of [3]-radialene. / Credit: The Lomonosov Moscow State University
The molecule the researchers are interested in is the dopant - a substance that is used to produce a desired electrical feature in a semiconductor, and in this case, to significantly increase the electrical conductivity of a polymer. Fluorinated dopants are what are currently used along with different organic semiconductors to intensify electrical conductivity, but some polymers used today in plastic electronics would not be suited to this pairing.

“Together with our Dresden colleagues we decided to design a completely new type of low molecular weight dopant for the organic semiconductor,” said Dmitry Ivanov. “And here it was important to choose a molecule that it was not only suitable in its energy levels, but, importantly, the dopant must be well mixed with the polymer, so that in contact with the polymer it does not segregate in a separate phase, eventually crystallizing and, in fact, losing contact with the polymer.”

This dopant, the derivative of [3]-radialene, is a small planar molecule that has a triangular structure from its carbon atoms. [3]-radialene was selected because it has the most suitable LUMO level, or the lowest unoccupied molecular orbital. Meaning that it can help to easily extract electrons from the semiconducting polymer matrix, thus becoming free charges and consequently increasing the conductivity of the doped material.

The researchers confirmed experimentally that this substance boosted the electrical conductivity of the polymer tremendously. “This could pave the way to fabrication of new organic solar cells with improved characteristics. We also think about production of organic field-effect transistors. I think it will give a significant boost to the development of organic electronic devices,” concluded Ivanov.

Sources: AAAS/Eurekalert! via Moscow State University, Advanced Materials
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