<b>I</b>n recent years, organic semiconductors (OSCs) have been of increasing interest for usage in photovoltaic devices owing to progress in device efficiencies. With the increased prevalence of OSC based devices on the market, there is a need to understand the oxidative and thermal stabilities of these materials for device lifetime maximization. In this work, we have chosen to investigate the thermal stability of a doped organic semiconductor system: poly-(3-hexyl-) thiophene (P3HT) doped with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). This particular system allows us to not only study possible chemical reactions that can be induced but also allows us to examine the relative thermal stabilities of the co-existent charge transfer states within the doped film. Using infrared spectroscopy of progressively heated thin films, we can directly probe the charge transfer state by monitoring key vibrational regions affiliated with the dopant as well as observe any newly formed bonds resulting from thermally induced chemical reactions. Comparing the resulting heated thin film spectra to results obtained from solution phase infrared spectroelectrochemistry and spectral calculations shows that the integer charge transfer (ICT) state of F4TCNQ reacts with the P3HT to from HF4TCNQ-, ultimately leading to a loss in conductivity. Furthermore, there is a dependence on environmental oxygen concentration that influences the rate of this reaction which allows for mechanistic insight into this thermally activated reaction process.

Spectroscopic investigation of thermally induced chemistry in doped organic semiconductor films

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.