(PEDOT-PSS)-carbon nanotubes composite films for Si solar cells

Carbon nanotubes-Si(CNTs-Si) Schottky solar cells have the advantages of low cost and facile fabrication. However, the applications of such devices have been limited by the low photovoltaic conversion efficiency, which is possibly derived from the high resistance of CNTs, non-uniform junction and serious light reflection. A composite film of poly(3,4-rethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS)-CNTs was prepared as a transparent conducting film for Si-based solar cell. The current-voltage curves show that the use of PEDOT-PSS considerably improves the conversion efficiencies from 5.9% for pristine CNTs-Si solar cells up to 11.6%. Aligned CNTs in the composite film facilitate the transfer of photo-generated holes in the junction region. The applied PEDOT-PSS conducting polymer fills the voids between nanotubes, improving the contact between CNTs and Si and forming additional Schottky junctions. A transparent polydimethylsiloxane (PDMS) film with an inverted pyramid structure was attached on the (PEDOT-PSS)-CNTs-Si solar cells, further improving the conversion efficiency to 12.4% by reducing light reflection loss. The electron beam induced current technique shows that the photo-conversion mechanism of such devices is based on a Schottky junction.