Improvement of organic photovoltaic cells (OPVs) performance requires the enhancement of photon absorption, dissociation efficiency of photo-generated excited states into separate charges and charge transport and collection.
In this communication, we report on OPVs with active layers composed of nanostructured films of a cross-linked photon-absorbing polymer, as electron-donor, and a soluble fullerene, as the electron-acceptor. We show that by modifying the structuring details of the polymer film, and therefore, of the donor/acceptor interface, the dissociation efficiency of photo-generated excitons (mostly within the polymer phase) into separate charges is affected, which, in turn affects OPV photo-current.
Although the performance of cells with such nanostructured donor/acceptor interfaces is still lower than that of cells based on blends of the same active components, the methodology employed in the fabrication of the polymer nanostructured films [1] represents an advantageous approach to achieve thermally stable and optimized film morphologies for OPV cells. Furthermore, this interdigitated donor/acceptor interface is the appropriate one to achieve efficient charge transport. If, using this approach, the nanostructuring dimensions can be decreased down to ca 25 nm (twice the exciton diffusion length), the cells may actually outperform those based on blends (the so called bulk heterojunctions).