Single-wall carbon nanotube/conjugated 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. (C) 2002 American Institute of Physics.