Hybrid solar cells based on single-walled carbon nanotubes/Si heterojunctions.

Photovoltaic devices based on single-walled carbon nanotubes (SWNTs) and n-silicon heterojunctions have been fabricated by a spray deposition process. We provide direct evidence that nanotubes serve as an active photosensing material involved directly in the photon absorption process as well as contributing to charge separation, transport and collection. The characteristic band of the SWNT band in the photoconductivity spectrum matches the S(11) absorption band of semiconducting SWNTs of 7,6 chirality. Centrifugation of the SWNTs provides two fractions. The sediment fraction exhibits a conversion efficiency ( approximately 1.7%) higher by a factor of eight compared to the supernatant fraction. SEM images and conductivity measurements show that the SWNT network morphology of the sediment fraction has longer and thicker nanotube bundles forming highly porous films, accounting for the enhanced conductivity and higher transparency.