TY - JOUR

T1 - Influence of processing and intrinsic polymer parameters on photochemical stability of polythiophene thin films

A1 - Vesterager Madsen,Morten

A1 - Tromholt,Thomas

A1 - Böttiger,Arvid P.L.

A1 - Andreasen,Jens Wenzel

A1 - Norrman,Kion

A1 - Krebs,Frederik C

AU - Vesterager Madsen,Morten

AU - Tromholt,Thomas

AU - Böttiger,Arvid P.L.

AU - Andreasen,Jens Wenzel

AU - Norrman,Kion

AU - Krebs,Frederik C

PB - Elsevier Ltd.

PY - 2012

Y1 - 2012

N2 - Intrinsic polymer parameters such as regio-regularity, molecular weight, and crystallinity play an important role when studying polymer stability. 18 different batches of poly-3-hexyl-thiophene (P3HT) were degraded in a solar simulator (AM1.5G, 1000 W/m2) and the degradation kinetics were monitored. The results suggest that the radical reaction responsible for the photodegradation takes place at terminal thiophene rings exposed at points were the conjugation is broken. This proposed mechanism is supported by the fact that stability scales with regio-regularity following the ratio of head-to-tail connected thiophene units. Annealing was found to relax the P3HT films and increase conjugation length and, in turn, increase stability observed as a delayed spectral blueshift caused by photochemical degradation. Crystallinity was found to play a minor role in terms of stability. Oxygen diffusion and light shielding effects were shown to have a negligible effect on the photochemical degradation rate. The results obtained in this work advance the understanding of polymer stability and will help improve the design of materials used for polymer solar cells resulting in longer lifetimes, which will push the technology closer to large-scale applications. © 2012 Elsevier Ltd. All rights reserved.

AB - Intrinsic polymer parameters such as regio-regularity, molecular weight, and crystallinity play an important role when studying polymer stability. 18 different batches of poly-3-hexyl-thiophene (P3HT) were degraded in a solar simulator (AM1.5G, 1000 W/m2) and the degradation kinetics were monitored. The results suggest that the radical reaction responsible for the photodegradation takes place at terminal thiophene rings exposed at points were the conjugation is broken. This proposed mechanism is supported by the fact that stability scales with regio-regularity following the ratio of head-to-tail connected thiophene units. Annealing was found to relax the P3HT films and increase conjugation length and, in turn, increase stability observed as a delayed spectral blueshift caused by photochemical degradation. Crystallinity was found to play a minor role in terms of stability. Oxygen diffusion and light shielding effects were shown to have a negligible effect on the photochemical degradation rate. The results obtained in this work advance the understanding of polymer stability and will help improve the design of materials used for polymer solar cells resulting in longer lifetimes, which will push the technology closer to large-scale applications. © 2012 Elsevier Ltd. All rights reserved.

KW - P3HT

KW - Photooxidation

KW - Organic photovoltaics

KW - Photo-chemical stability

KW - Degradation

U2 - 10.1016/j.polymdegradstab.2012.07.021

DO - 10.1016/j.polymdegradstab.2012.07.021

JO - Polymer Degradation and Stability

JF - Polymer Degradation and Stability

SN - 0141-3910

IS - 11

VL - 97

SP - 2412

EP - 2417

ER -