Igor Zozoulenko, professor and head of the theory and modelling group at the Laboratory of Organic Electronics at Linköping University. Photo: Peter Holgersson.The conducting organic polymer PEDOT (poly(3,4-ethylenedioxythiophene)) is probably one of the world's most intensely studied materials. Despite this, researchers at Linköping University in Sweden have now demonstrated that the material functions in a completely different manner than previously believed. This finding could have huge significance for many applications.
More than 1500 scientific papers are devoted each year to PEDOT, making it probably one of the world's most intensely studied materials. This polymer has unique properties, and is highly suitable for use in solar cells, electrodes, light-emitting diodes, soft displays, bioelectronic components and many other applications. However, most of these papers are experimental in nature, and only a tiny fraction – fewer than one in 1000 – provide a theoretical understanding of various aspects of the polymer, including its electronic structure.
"The age of trial and error research should be over. I cannot imagine how it would be possible today to develop a new material without having a deep theoretical understanding of the underlying principles that determine its properties," says Igor Zozoulenko, professor and head of the theory and modelling group at the Laboratory of Organic Electronics at Linköping University.
Zozoulenko is the main author of a paper in ACS Applied Polymer Materials that presents a new theory for the electronic structure and optical properties of PEDOT. This theory overturns a lot of previous research on PEDOT.
The calculation model currently recognised as the most accurate for predicting the properties of materials is density functional theory (DFT). This model calculates quantum mechanical electron densities in the most efficient way possible, and has become a standard within various branches of materials science. For organic conducting polymers, however, models developed in the 1980s – before DFT gained widespread use – are still widely utilized. The work of the researchers at Linköping University has now shown that these models are clearly erroneous.
"Many of the analyses that have been presented in scientific articles about PEDOT will have to be re-visited and revised," says Zozoulenko.
One of the major differences concerns the optical absorption properties of the material, which are, of course, crucial for its use in solar cells, soft displays and other applications. The optical absorption spectra – the color of the light – depends on the electronic structure of PEDOT, including such properties as the energy levels at which electrons are located inside the atom, the spins they possess, and the way in which they can move in the material. Since scientists’ understanding of optical absorption has been deficient up to now, their interpretation of their experimental results has been wrong.
"Our paper presents a completely different interpretation of the optical spectra from PEDOT, and a completely different interpretation of the electron parametric resonance spectrum," says Zozoulenko. "Our results can also be applied to many other conducting polymer materials."
This story is adapted from material from Linköping University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.