Carbon nanotubes and graphene represent attractive materials for photovoltaic devices. Single wall carbon nanotubes (SWNTs) bear many superior properties for photovoltaic application such as a wide range of direct bandgaps matching the solar spectrum, strong photoabsorption from infrared to ultraviolet, high carrier mobility, and reduced carrier transport scattering. SWNTs can be directly configured as energy conversion materials to fabricate thin-film solar cells, with nanotubes serving as both photogeneration sites and charge carriers collecting/transport layers. SWNTs can be modified into either p-type conductor through chemical doping (like thionyl chloride, or just exposure to air) or n-type conductor through polymer (like polyethylene imine) functionalization. The solar cells consist of either a semitransparent thin film of p-type nanotubes deposited on an n-type silicon wafer or a semitransparent thin film of n-type SWNT on p-type substrate to create high-density p-n heterojunctions between nanotubes and silicon substrate to favor charge separation and extract electrons and holes. The high aspect ratios and large surface area of nanotubes could be beneficial to exciton dissociation and charge carrier transport thus improving the power conversion efficiency. Another prototype employ the use of conducting polymeric materials combined with graphene layers to achieve higher efficiency of such photovoltaic devices. A higher dissociation/transportation of the charge carriers is expected for such nanocomposite materials while used as p/n layers.
Journal: TechConnect Briefs
Volume: 1, Nanotechnology 2010: Advanced Materials, CNTs, Particles, Films and Composites
Published: June 21, 2010
Pages: 274 - 277
Industry sector: Advanced Materials & Manufacturing
Topics: Carbon Nano Structures & Devices