Near-infrared photoresponse in single walled carbon nanotube/polymer composite films

We present a near-infrared photoresponse study of single-walled carbon nanotube/poly(3-hexylthiophene)-block-polystyrene polymer (SWCNT/P3HT-b-PS) composite films for different loading ratios of SWCNT in the polymer matrix. Compared to the pure SWCNT film, the photoresponse [(light current -- dark current)/dark current] is much larger in the SWCNT/polymer composite films. The photoresponse is up to 157{\%} when SWCNTs are embedded in P3HT-b-PS while for a pure SWCNT film it is only 40{\%}. We also show that the photocurrent strongly depends on the position of the laser spot with maximum photocurrent occurring at the metal--film interface. We explain the photoresponse due to exciton dissociations and charge carrier separation caused by a Schottky barrier at the metallic electrode - SWCNT interface