L. Yu, D. Tune, J. Shapter
Keywords: SWCNT, solar cells, nanotube-silicon heterojunction
Summary:Due to the high cost of silicon photovoltaics there is currently great interest in finding alternative semiconductor materials for light harvesting devices. Single walled carbon nanotubes (SWCNTs) are an allotrope of carbon having unique electrical and optical properties. It is important to investigate methods of exploiting these properties in photovoltaic devices. Ironically, one way to do this is to combine them with a well understood model semiconductor such as silicon. Nanotube-silicon heterojunction (NSH) solar cells are a recent photovoltaic architecture with demonstrated power conversion efficiencies of up to 17 %. This talk will focus on hybrid solar cell devices of a thin film of polyaniline deposited on silicon and covered by a SWCNT film. These hybrid devices combine the conformal coverage given by the polymer and the excellent electrical properties of SWCNT films and significantly outperform either of their component counterparts. Treatment of the silicon and carbon nanotubes with hydrofluoric acid and the strong oxidiser, thionyl chloride, leads to a significant improvement in performance. Additionally polymer layers have been added to NSH cells as a top antireflection layer. Efficiencies of about 7.8% have been obtained by adding polystyrene (75 nm) as the antireflection layer on top of the SWCNT film.