Compartmentalization is a fundamental strategy in building complex hierarchical nano-devices, but understanding communication between distinct molecular architectures will be essential for their operation. Structurally well-defined aggregates, especially artificial vesicles possessing adequate size and stability, may play an important role in future electronic devices, where they can serve to compartmentalize function inside hollow spheres. Thanks to a previous Orchid (PHC 2007 ? 08) project between the two coordinating partners (Bassani, ISM and Wong, NTU), the French and Taiwanese teams established a novel one-step methodology for preparing conjugated ?-structures possessing biuret molecular recognition motifs. In addition to its inherent simplicity and versatility, this methodology does not require the introduction of an inert spacer between the aromatic core and the biuret units. We believe that the absence of a flexible spacer is responsible for the unusual self-assembly properties of these materials: Preliminary investigations showed that these highly luminescent compounds posses the inherent ability to spontaneously self-assemble into vesicles when dissolved in organic solvents. Unlike other examples of vesicle-forming conjugated compounds, the presence of long alkyl substituents or ionic head groups ? both deleterious to charge transport ? is not required. Furthermore, the vesicles are formed spontaneously, without external energy (heating or sonication), or special procedures. During the course of the project, we will pursue methods for controlling the deposition of these light-emitting vesicles on insulating and on conductive surfaces (ITO, metallic surfaces, doped Si). The French partner ISM will investigate information transfer within and in-between immobilized vesicles (exciton migration, charge transport) using state-of-the-art time-resolved confocal fluorescence microscopy. A second French partner, CEA, will study the mechanisms driving vesicle formation in organic media thanks to advanced characterization techniques including X-ray and neutron scattering. Synthesis will be carried out by the Taiwanese partner at NTU, whose previous results showed that it is possible to tailor the electronic energy levels of the vesicles by small modifications of the conjugated core. The resulting compounds will not only cover the entire visible spectrum in terms of fluorescence emission, but will also be suitable to investigate energy transfer processes between individual vesicles. Concomitantly, the electronic properties of the materials will be explored, with special attention to the possibility of employing the vesicles as individual pixels in future OLED displays. The latter would boast unprecedented resolution and would be interesting for miniature displays placed close to the eye, or in embedded systems requiring miniaturization. Two Taiwanese teams, Academia Sinica and Electrical Engineering (NTU), will undertake complete characterization of the electronic properties of material down to the single object level. Together, they possess the know-how and advanced instrumentation (ambient SEM, conducting- and Kelvin force AFM, STM, SNOM) required. We expect these ambitious goals to allow us to significantly and durably advance the field of self-assembled molecular nanotechnology. Thanks to OLEV, we will be able to (i) investigate the electronic properties of vesicles devoid of tunnelling barriers caused by the presence of long alkyl chains; (ii) elucidate the mechanisms of spontaneous self-organization of electroactive moieties into functional assemblies; (iii) investigate electronic communication between nanometric supramolecular assemblies mediated by electron transfer and exciton migration; (iv) Probe the electronic characteristics (conductivity, I/V, electroluminescence, etc.) of individual assemblies. By constructing an ensemble of electro-active compounds designed to self-organize into specific supramolecular aggregates, we will be able to rapidly explore a wide range of combinations in terms of electronic and spectral properties, allowing us to quickly identify and focus on systems displaying interesting properties, such as efficient charge transport or fast exciton migration.

The overall Photovoltaic (PV) industry grows by more than 30 % per year and the market volume is expected to reach over 20 billion Euros in 2010. Most of the technology in the field is based on silicon solar cells today. On the other hand, III-V multi-junction solar cells are reaching significantly higher solar to electric conversion efficiencies exceeding 40 %. These solar cells are widely used for powering satellites and recently also the promising terrestrial market of concentrator PV is starting to grow rapidly. These systems make use of the highest efficiency III-V multi-junction solar cells under an optical concentrator such as a Fresnel lens, concentrating the sunlight by a factor of 500-1000. In this way the area of expensive III-V semiconductor material is greatly reduced by the use of cheaper optical elements. Still, the solar cell accounts for approximately 20 % of the system costs.Therefore, reducing the cost of the multi-junction solar cell as well as increasing their conversion efficiency are important strategies for achieving the goal of making this technology competitive to conventional energy sources in the future. In the project “SolarBond”, we are aiming to develop and demonstrate a new alternative substrate technology which allows growing high-efficiency GaAs based solar cells with excellent crystal quality and to remove the substrate afterwards in a simple lift off process. To achieve this, the alternative substrate will provide a thin monocrystalline layer,i.e. an epitaxial template for the solar cell, on top of a temporary handle substrate. In between, a buried lift off layer will be incorporated allowing removing the solar cell after its growth from the substrate. Both the initial substrate, providing the thin monocrystalline layer, and temporary handle will be recycled, thus saving expensive material and allowing reducing the substrate cost.