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Updated: May 22, 2026

A 3D-printed Chamber for Organic Optoelectronic Device Degradation Testing
Published on: August 10, 2018
Degradation mechanism of benzodithiophene-based conjugated polymers when exposed to light in air
Salima Alem1, Salem Wakim, Jianping Lu
1Institute for Microstructural Sciences and ‡Institute for Chemical Process and Environmental Technology, National Research Council of Canada , 1200 Montreal Road, Ottawa, Ontario K1A 0R6, Canada.
Abstract:
We report the investigation of the air photostability of benzo[1,2-b:4,5-b']dithiophene (BDT) based conjugated polymers using UV-visible spectroscopy, X-ray photoelectron spectroscopy, gel permeation chromatography, and nuclear magnetic resonance spectroscopy. Three low band gap alternating D-A copolymers consisting of 3-fluoro-2-heptylcarbonylthieno[3,4-b]thiophene and alkyl-substituted BDT, alkoxy-substituted BDT, or dithienosilole, respectively, were prepared for investigating their photovoltaic performance and photostability. After only two hours of simultaneous exposure to light and air, the main absorption peak of the polymer films containing BDT units blue-shifted and its intensity dramatically decreased. We demonstrated that the BDT unit underwent dramatic structural change under illumination in air by reacting with the oxygen molecules at the excited state, leading to the disruption of the main-chain conjugation of the polymer. As a result, the color of the alkyl-BDT based polymer film permanently changed from deep blue to light yellow. In contrast, the dithienosilole based polymer was quite stable when treated under the same condition with negligible change in the absorption spectrum.
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