Harvesting infrared solar energy by semiconducting single-walled carbon nanotubes

Semiconducting single-walled carbon nanotubes (S-SWNTs) are used to fabricate p-n heterojuctions with n-type Si in order to harvest nearinfrared solar energy. Our results demonstrate that S-SWNTs can be used to convert near-infrared light into electrical energy. The performance of solar cells based on C₆₀-fullerene-encapsualted S-SWNTs is much better than that observed in solar cells fabricated by C₆₀-encapsulated SWNTs containing both metallic and semiconducting SWNTs. It is found that when the light photon energy exceeds two times the band-gap energy of S-SWNTs, the efficiency suddenly increases, suggesting the occurrence of multiple exciton generation.