• Energy Research

The growth of nanohybrids synthesized by supersonic beam codeposition of metal oxide clusters, produced by microplasma cluster source, and of aerodynamically accelerated molecules has been explored as a novel approach to the preparation of controlled dye sensitized materials for photovoltaic applications. The hybrid nanostructures are formed through deposition via supersonic expansion processes, controlling the kinetic energy of the precursors. With this approach, we developed prototype dye sensitized solar cells based on nanostructured TiO2 and CuPc with different architectures. To explore the viability of this approach, we compare cells made layer by layer with those where an intermediate codeposited layer is inserted between the two raw materials. This latter type of cells presents an enhancement of the photocurrent of a factor of 45 and of the efficiency of a factor of 40. This work opens a new viable perspective in the growth and in the control of the interfacial properties of nanohybrid materials, by direct codeposition of molecules and oxide nanostructures, with demonstrated useful applications in photovoltaic devices.

It is shown that morphology and structure of films of oligothiophenes can be controlled well via supersonic molecular beam epitaxy (SuMBE). The supersonic expansion of oligomers seeded in inert gases makes it possible to tune beam parameters such as kinetic and internal energy, momentum and flux in a range that is shown to play a critical role in the morphology of the surface of the films. By simply varying the seeding in the source, we change the initial state of the oligomers in the beam. In this way, very different morphologies are obtained, ranging from a dendritic-like, typical of a disordered growth, to ordered layered structures. In this case the terraces observed were characterized by widths on a micron scale and height equal to the molecular length. This last morphology, studied by Atomic Force Microscopy in the tapping mode, is consistent with X-ray diffraction data and the optical response of the same films. These properties are maintained up to unprecedented film thicknesses (>=500 nm).