Max Shtein, advisor

Organic photovoltaic (OPV) cells have recently emerged in the last decade as a viable alternative to contemporary solar cells for power generation due to their low cost, compatibility with low- temperature and high-throughput processing methods, compatibility with flexible and stretchable substrates, low toxicity, and elemental abundance. Unlike inorganic materials, organic molecules exhibit narrow absorption bands, and photocurrent generation in OPVs generally is limited by poor optical absorption across the solar spectrum. This is further compounded by the short exciton diffusion length (LD) in most organics compounds (~10 nm) which is an order of magnitude lower than the absorption depth (~100 nm). As a result, planar OPV active layer thicknesses must be approximately equal to LD to ensure efficient diffusion of photogenerated excitons to a heterojunction, where dissociation into free charges occurs. In this defense, we examine multiple techniques to circumvent the fundamental tradeoff between absorption and diffusion in OPVs by modifying the structure of the active layers and by enhancing optical coupling.