Solar Energy Materials & Solar Cells 90 (2006) 2777–2792
Lifetimes of organic photovoltaics: Design and
synthesis of single oligomer molecules in order to
study chemical degradation mechanisms
Jan Alstrup, Kion Norrman, Mikkel Jørgensen, Frederik C. Krebs
The Danish Polymer Centre, RISØ National Laboratory, P.O. Box 49, DK-4000 Roskilde, Denmark
Received 5 November 2005; accepted 17 April 2006
Available online 14 June 2006
Degradation mechanisms in organic and polymer photovoltaics are addressed through the study of
an organic photovoltaic molecule based on a single phenylene–vinylene-type oligomer molecule. The
synthesis of such a model compound with different end-groups is presented that allows for
assignment of degradation products from different parts of the molecule. Photovoltaic devices with
and without C
have been prepared and their characteristics under AM1.5 conditions are reported.
The degradation of the active phenylene–vinylene compound in darkness and after 20 h of
illumination were investigated using a mass spectrometric technique (time-of-ﬂight secondary ion
mass spectrometry) allowing elucidation of the oxidative degradation pathways.
r 2006 Elsevier B.V. All rights reserved.
Keywords: Organic; Polymer; Oligomer; Photovoltaics; Degradation; Lifetime; TOF-SIMS; Mechanisms
The use of organic materials and polymers in organic photovoltaics [1–6] have been
investigated in numerous reports due to the promise of low-cost ﬂexible photovoltaics with
low thermal budgets, low production cost and fast solution-phase processing using various
coating techniques [7–9]. Recently efﬁciencies approaching 5% has been indicated for
small area photovoltaics [10,11] and while this efﬁciency is more than sufﬁcient for many
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