Single-wall carbon nanotubeÕconjugated polymer photovoltaic devices

We report the optoelectronic properties occurring in single-walled carbon nanotubes ~SWNTs!— conjugated polymer, poly~3-octylthiophene! composites. Composite films were drop or spin cast from a solution on indium–tin oxide ~ITO! and quartz substrates and studied using absorption spectroscopy and electrical characterization methods. Diodes ~Al/polymer-nanotube composite/ ITO! with a low nanotube concentration (,1%) show photovoltaic behavior, with an open circuit voltage of 0.7–0.9 V. The short circuit current is increased by two orders of magnitude compared with the pristine polymer diodes and the fill factor also increases from 0.3 to 0.4 for the nanotube/ polymer cells. It is proposed that the main reason for this increase is the photoinduced electron transfer at the polymer/nanotube interface. The results show that the conjugated polymer-SWNTs composite represents an alternative class of organic semiconducting material that is promising for organic photovoltaic cells with improved performance. © 2002 American Institute of Physics. @DOI: 10.1063/1.1428416#