Stability Study on Anion exchanged Donor-Acceptor based co-polymers

Semiconducting Polymers (SPs) have received widespread attention due to their promising qualities like superior absorbance/emission, easy chemical tunability, low-temperature solution processing, lightweight and flexible substrates, and low environmental toxicity. Molecular doping of SPs has been one of the most popular research topics in organic electronics over the past few decades. FeCl₃ is a well-known p-type molecular dopant for SPs. Recently a new technique was introduced that is known as anion exchange that involves replacing the counter ion in a doped polymer with a more stable one to improve the longevity of the SP film. We show a D/A type co-polymer immersed in a dopant solution containing FeCl₃ and the ionic liquid, LiTFSI. TFSI⁻ counter ion is hydrophobic, stable under oxidizing conditions and weakly interacting with most cations. Under favorable conditions, TFSI^- replaces the less stable FeCl₄^- counter ion. The main aim of this work is to study the degradation of SP films that are doped with FeCl₃ vs that are anion exchanged. We perform experiments that include UV-Vis-NIR spectroscopy, 4-proble sheet resistance and Gas Chromatography-Mass Spectroscopy and X-Ray Absorption Spectroscopy to contrast the degradation between the two doped films.