Abstract
The development of solar cells based on composites of organic conjugated semi-conducting
polymers with fullerene derivatives can provide a new method in the exploitation of solar energy. Organic
solar cells must fulfill the criteria of stability, efficiency and reduction of production costs to find new
applications. Specially, the bulk donor-acceptor heterojunctions between conjugated polymers and fullerenes
have been successfully utilized for photovoltaic devices with high carrier collection efficiency compared
to the devices made from single components. In this work we present measurements of the photovoltaic
response of bulk donor-acceptor heterojunction between the conjugated polymer (as a donor, D) poly(3-
octylthiophene), P3OT and fullerenes, (as acceptor, A), deposited between indium tin oxide and aluminum
electrodes. These devices are based on ultrafast, reversible, metastable photoinduced electron transfer and
charge separation.The quality and homogeneity of composite films as well as the choice of the substrates strongly influence
the efficiency of the solar cells. One of the most important limiting factors in the performance of
this present types of molecular solar cells based on interpenetrating networks of conjugated polymers and
fullerene derivatives is the charge carrier transport in the active layer. This transport is driven by the electrical
field provided externally by the top and bottom electrodes with different work functions. We present here
efficiency and stability studies on large area (6 cm