Photovoltaic properties of dye functionalized single-wall carbon nanotube/conjugated polymer devices

Photovoltaic properties of dye, N-(1-pyrenyl)maleimide (PM), functionalized single-walled carbon nanotubes (SWNT)-conjugated polymer, poly(3-octylthiophene) (P3OT), blend composites are reported. Devices were fabricated by drop or spin cast from the solution of composite onto ITO-coated glass. Improved performance was achieved by functionalizing the SWNT with dye molecules. Photovoltaic behavior with an open circuit voltage of 0.6-0.7 V was measured in diodes (Al/SWNT+PM-polymer/ITO). The short circuit current was found to increase by more than an order of magnitude compared to the SWNT-polymer diode without dye. Optical absorption spectra showed considerable ground-state interaction between SWNT+dye and the polymer. It is proposed that the main reason for the increase in short circuit current is due to efficient transfer of holes by dye molecules to P3OT at the dye/polymer interface and the rapid transfer of the generated electrons to the SWNTs at the dye/nanotube interface. It is shown that the dye functionalized SWNT-conjugated polymer composites represent an alternative class of organic semiconducting materials for dye-based organic photovoltaic cells.