Photostability in dioxyheterocycle electrochromic polymers

Many proposed applications for electrochromic polymers (ECPs), which are designed to modulate the intensity or spectral power density of light, center around the interaction between the ECPs and the incident light. The long-term effects of the interaction of light and ECPs are rarely discussed in the literature, yet is a crucial parameter in materials evaluation in many applications. With the goal of examining the photo-stability of select ECPs, two polymers were selected for study, which are representative of both 3,4-dioxythiophene (DOT) and 3,4-dioxypyrrole (DOP) based materials. Samples of each material were sealed in glass cells under varying atmospheric conditions using a polyisobutylene-based barrier sealant and irradiated under a solar simulator for time periods ranging from 24 hours to one month. Following irradiation, electrochromic performance was assessed via both electrochemical and spectroelectrochemical methods. Additionally, X-ray photoelectron spectroscopy (XPS) was used to study chemical changes following irradiation. We report here that, following irradiation, no change in electrochromic performance (as measured by Delta%T at lambda(max)) nor spectra recorded via XPS was observed in films encapsulated under an inert atmosphere, suggesting that conditions of irradiation alone are insufficient to degrade the performance of either ECP structure.