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
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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
Abstract
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
60
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
1. Introduction
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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doi:10.1016/j.solmat.2006.04.004
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Corresponding author. Tel.: +45 46 77 47 99; fax: +45 46 77 47 91.
E-mail address: frederik.krebs@risoe.dk (F.C. Krebs).