Introduction
Photovoltaic cells (PVs) based on conjugated polymers rely on excited state charge transfer (between electron donors and electron acceptors) and charge collection by the electrodes. In order to improve their power conversion efficiency, efficient photon absorption, high interfacial areas between donor and acceptor to promote efficient exciton dissociation and efficient percolation paths for the photogenerated charges are being investigated. Donor/acceptor bi-layers and bulk heterojunctions are the two main/extreme device structures being used. While the first optimises the charge transport, the second optimises exciton formation and dissociation. Donor/acceptor interdigitated columnar structures are an intermediate case, which has been proposed as a possible compromise between the two extreme cases. However, columnar structures with diameters on the order of twice the exciton diffusion length are not easy to form with conjugated polymers.
In this communication we report on surface structuring of cross-linkable polymer films and their use in the fabrication of PVs aiming to improve the interfacial area with a fullerene electron acceptor.