Photovoltaic Applications of Silicon Nanocrystal Based Nanostructures Induced by Nanosecond Laser Fragmentation in Liquid Media

Silicon nanocrystals (Si-ncs) with quantum confinement properties represent an attractive photovoltaic material. The ability to collect the photogenerated current through efficient electronic transport and exciton dissociation is a current challenge for the deployment of Si-nc based solar cells. We report here on prospective and cost-effective approaches to engineer the surface of electrochemically etched Si-ncs by laser fragmentation in ethanol and water. The properties of the engineered Si-ncs have been analyzed in detail by photoluminescence and absorption measurements together with Fourier transform infrared spectroscopy. To demonstrate the advantageous attributes of Si-nc surface engineering in liquid media, a few photovoltaic devices based on different architectures have been fabricated. First, anatase TiO2 nanotubes have been used as a host template for laser-fragmented Si-ncs to form inorganic-sensitized solar cell architectures. Second, we have produced bulk-heterojunction solar cells with a Si-nc/fullerene photoactive interface. This design has been further improved by functionalizing the Si-nc surface with water-soluble poly(3,4-ethylenedioxythiophene), i.e., PEDOT. All the devices produced here have been characterized with external quantum efficiency measurements, and in some cases the current voltage characteristic has been also measured.