Novel Solar Cells Using Carbon Materials

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 are an allotrope of carbon having unique electrical and optical properties and are promising as future photovoltaic materials.  It is thus important to investigate methods of exploiting their properties in photovoltaic devices.  Ironically, one way to do this is to combine them with a relatively well understood model semiconductor such as silicon.  Nanotube-silicon heterojunction solar cells are a recent photovoltaic architecture with demonstrated power conversion efficiencies of up to 14 % that may in part exploit the photoactivity of carbon nanotubes.  

Silicon solar cell devices fabricated with a thin film of the conductive polymer, polyaniline, have been reported but these devices can suffer from poor performance due to the limited lateral current carrying capacity of very thin polymer films.  This talk will focus on hybrid solar cell devices of a thin film of polyaniline deposited on silicon and covered by a single walled carbon nanotube film are fabricated and characterised.  These hybrid devices combine the conformal coverage given by the polymer and the excellent electrical properties of single walled carbon nanotube 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.