Nanopatterned organic materials for photovoltaic devices

In order to further increase the efficiency of current state-of-the-art photovoltaic devices, the interfacial architecture must be controlled at the nanoscale such that the donor/acceptor (D/A) blend results in an ideal morphology for maximizing charge collection efficiency. The ideal bulk heterojunction (BHJ) consists of an interpenetrating network such that every exciton formed is within a diffusion length of the D/A interface and there are straight pathways to the respective electrodes. In light of this ideal structure goal, we have fabricated patterned bilayer photovoltaic (PV) cells using a perfluoropolyether (PFPE) elastomeric stamp to control the morphology of the donor-acceptor interface within devices. Specifically, devices were fabricated using the Pattern Replication In Non-wetting Templates, or PRINT, process to have nanoscale control over the bilayer device architecture. This "top-down" approach allows for facile patterning over large areas. The low-surface energy, chemically resistant, variable modulus, fluoropolymer based molds used in PRINT provide a route to patterning a variety of materials. We have focused on patterning organic based materials systems which have been used in current BHJ devices. Ordered, sub-100 nm structures have been fabricated over large areas to investigate the effect of nanopatteming on PV-performance.