Core-Shell Nanostructures of Organic-Inorganic Nanomaterials for Hybrid Photovoltaics

Ordered bulk heterojunctions in hybrid photovoltaics show great promise towards high efficiency devices. We report ordered core-shell nanostructures of organic-inorganic nanohybrids processed from solution. Inorganic semiconductor nanowires are prepared by facile solvothermal synthesis. High aspect ratio of the nanowires is controlled by optimizing reaction parameters. Core-shell nanohybrids are synthesized by side-on grafting conjugated polymers onto the inorganic nanowires. We demonstrate that high aspect ratio nanowires and their core-shell nanohybrids spontaneously form liquid crystalline phases in solution. These systems show isotropic, bi-phasic and nematic phases with an increase of concentration, which is in reasonable agreement with Onsager’s theory for rigid rodlike liquid crystals. Suspensions are readily processed to produce ordered aligned films with large-area monodomains. It is found that the conjugated polymer forms an ordered crystalline layer on the nanowire, as opposed to its noncrystalline bulk counterpart. The side-on grafting of polymers on the nanowires results in aligned chain-extended backbones along the nanowire long axis in contrary to the chain-folded backbones by end-on grafting of polymers. Decreasing the nanowire diameter tends to increase the chain-extended conjugated length. Such uniaxially aligned, fully chain-extended, highly ordered crystalline polymer nanostructures across interface could significantly enhance electron transfer, charge transport and collection. The corresponding optoelectronic properties are addressed.