PHOTOSI · Silicon nanocrystals coated by photoactive molecules: a new class of organic-inorganic hybrid materials for solar energy conversion

Silicon nanocrystals (SiNCs) have gained much attention in the last few years because of their remarkable optical and electronic properties, compared to bulk silicon. These unique properties are due to quantum confinement effects and are thus strongly dependent on the nanocrystal size, shape, surface functionalization and presence of defects.The aim of the present project is the coupling of SiNCs with photo- and electroactive molecules or multicomponent systems, like dendrons, to build up a new class of hybrid materials to be employed in the field of light-to-electrical energy conversion (solar cells).SiNCs possess several advantages with respect to more commonly employed, quantum dots, which usually contain toxic and rare metals like lead, cadmium, indium, selenium: a) silicon is abundant, easily available and essentially non toxic; b) silicon can form covalent bonds with carbon, thereby offering the possibility of integrating inorganic and organic components in a robust structure; c) absorption and emission can be tuned across the entire visible spectrum from a single material, upon changing the nanocrystal dimension.This project will address the understanding of the fundamental photophysical and electrochemical properties of SiNCs, and their electronic interactions with the functional coating units. Taking advantage of the acquired knowledge, the project will then be devoted to the implementation of these hybrid materials as light-harvesting and charge transport components in photoelectrochemical cells. PhotoSi is expected to lead to solar cells with high efficiency (superior electronic properties of the hybrid material), low cost (the amount of the nanostructured material is significantly reduced compared to conventional Si cells), and low environmental impact (Si is essentially non toxic, and new less-energy demanding synthetic methodologies will be explored).