Organic photovoltaic represents an emerging technology thanks to its ability to give flexible, light weight and large-area
devices, with low production cost by simple solution process or printing technologies. But these devices are known to
exhibit low resistance to the combined action of sunlight, oxygen and water. This paper is focused on the behaviour of
the active layer of the devices under illumination in the presence and absence of oxygen.
The monitoring of the evolution of the chemical structure of MDMO-PPV submitted to accelerated artificial ageing
permitted the elucidation of the mechanisms by which the polymer degrades. Extrapolation of the data to natural ageing
suggested that, if well protected from oxygen (encapsulation),
MDMO-PPV:PCBM based active layer is
photochemically stable for several years in use conditions. In addition the charge transfer between the two materials was
observed to remain efficient under exposure.
The study of P3HT:PCBM blends allowed to point out the Achilles heel of P3HT towards the impact of light. In
addition, P3HT:PCBM blends were shown to be much more stable under illumination than MDMO:PCBM blends.
Preliminary results devoted to the AFM monitoring of the morphological modifications of P3HT:PCBM blends under
the impact of light are also reported.