Lifetimes of organic photovoltaics: Design and synthesis of single oligomer molecules in order to study chemical degradation mechanisms

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 C60 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.