Silicon nanocrystal surface engineering and their electronic interaction with carbon based materials

Hybrid nanomaterials that consist of silicon nanocrystals (Si-ncs) and carbon-based nanostructures (i.e. nanotubes, fullerenes C₆₀, etc.) may represent a new class of materials for photovoltaics (PV) with potential for improvements in efficiency and ease of device integration. In this contribution we present results on photovoltaic applications of surfactant-free, quantum confined and surface-engineered Si-ncs combined with semiconducting single walled carbon nanotubes (SWCNTs) or C₆₀. We show that both types of carbon-based nanomaterials allow for electronic interactions with the Si-ncs. Firstly, the electronic interactions between Si-ncs and purified semiconducting SWCNTs has shown opto-electronic conversion over a large spectral range (300-1600 nm). but, in order to enhance interface interactions, the accurate control of Si-ncs surface properties is essential. Secondly, our approach to achieve effective Si-ncs surface engineering is based on nanosecond pulsed laser processing in liquid media. We provide evidence that laser processing in water induces Si-ncs dipole-dipole surface interactions that result in self-organized Si-ncs patterns. The subsequent deposition of a C₆₀ nano-layer on the Si-ncs forms a bulk-type heterojunction. Solar cell devices made out of these surface-engineered Si-ncs and the C₆₀ nano-layer showed photovoltaic action with increased conversion efficiency due to Si-ncs surface engineering.