The mechanism of photo- and thermooxidation of poly(3-hexylthiophene) (P3HT) reconsidered

Poly(3-hexylthiophene) (P3HT) has been the focus of great interest as it is widely used in organic solar cells. However, P3HT has relatively poor photochemical and thermal stability under ambient atmosphere, which leads to a reduced lifetime of the solar cells. It was therefore necessary to study th...

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Bibliographic Details
Published in:Polymer degradation and stability 2009-06, Vol.94 (6), p.898-907
Main Authors: Manceau, Matthieu, Rivaton, Agnès, Gardette, Jean-Luc, Guillerez, Stéphane, Lemaître, Noëlla
Format: Article
Language:English
Subjects:
Ageing
Applied sciences
Chemical Sciences
Degradation
Exact sciences and technology
Infrared spectroscopy
Organic photovoltaic
Physical properties
Poly(3-hexylthiophene)
Polymer industry, paints, wood
Polymers
Properties and testing
Technology of polymers
UV-visible light irradiation
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Summary:Poly(3-hexylthiophene) (P3HT) has been the focus of great interest as it is widely used in organic solar cells. However, P3HT has relatively poor photochemical and thermal stability under ambient atmosphere, which leads to a reduced lifetime of the solar cells. It was therefore necessary to study the photo- and thermooxidation of P3HT. Thin P3HT films were exposed to UV–visible light irradiation and thermal ageing, both in the presence of air. Changes in the infrared spectra of the aged samples were recorded, and the oxidation products were identified. A degradation mechanism that accounted for the modifications in the infrared spectra was then developed. This mechanism confirmed that singlet oxygen plays no decisive role, as previously reported. Oxidation was shown to involve the radical oxidation of the n-hexyl side-chains and the subsequent degradation of the thiophene rings. The breaking of the macromolecular backbone resulted in a loss of π-conjugation, provoking the bleaching of the sample.
ISSN:0141-3910
1873-2321
DOI:10.1016/j.polymdegradstab.2009.03.005