The unique properties of semiconducting single-walled carbon nanotubes (s-SWCNTs) offer significant advantages over organic molecules, semiconducting polymers, and solid-state semiconductors for wide ranging applications. In particular, s-SWCNT are potentially highly effective active absorption layers in thin-film solar cells because the optical absorption bands—that depend on the chiral indices, (n,m)—of s-SWCNTs exhibit excellent overlap with the useful solar spectrum range of the sun’s radiation.