By Josh Perry, Editor
[email protected]

Researchers from Linkoping (Sweden) University (LiU) revealed new properties from the frequently studied organic polymer poly(3,4-ethylenedioxythiophene), commonly known as PEDOT, which is used in a number of applications from solar cells to LED to bioelectronic components and more.

PEDOT, which is a common organic polymer, has a number of applications including solar cells. (Wikimedia Commons)

According to a report from the university, LiU researchers have disproven the common calculation tools for predicting the properties of organic materials, which were created prior to the adoption of density functional theory (DFT). DFT “calculates quantum mechanical electron densities in the most efficient way possible.”

The primary difference between the new research and previous calculation tools for PEDOt is related to the light-emitting properties of the material.

“The optical spectrum – the color of the light – depends on the electronic structure of the material, 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,” the article said. “Since our understanding has been deficient, the interpretation of the experimental results has been wrong.”

The research was recently published in Applied Polymer Materials. The abstract stated:

“Electronic structure and optical absorption spectra of poly(3,4-ethylenedioxythiophene) (PEDOT) for different oxidation levels were studied using density functional theory (DFT) and time-dependent DFT. It is shown, that the DFT-based predictions for the polaronic and bipolaronic states and the nature of corresponding optical transitions are qualitatively different from the widely used traditional picture based on semi-empirical pre-DFT approaches that still dominate the current literature.

“On the basis of the results of our calculations, the experimental Vis/NIR absorbance spectroscopy and the electron paramagnetic resonance spectroscopy are re-examined, and a new interpretation of the measured spectra and the spin signal, which is qualitatively different from the traditional interpretation, is provided.

“The findings and conclusions concerning the nature of polaronic and bipolaronic states, band structure and absorption spectra presented for PEDOT, are generic for a wide class of conducting polymers (such as polythiophenes and their derivatives) that have a similar structure of monomer units.”