Solar Cells Based on Composites of Donor Conjugated Polymers and Carbon Nanotubes

In this chapter, the photovoltaic properties occurring in single-wall carbon nanotubes (SWNTs)–donor conjugated polymer composites are reported. Photovoltaic devices based on the dispersed heterojunction concept, containing a blend of SWNTs and soluble poly(3-octylthiophene) (P3OT) were studied. The nanotubes not only act as electron acceptors, but also allow the electrons to transport efficiently along their length. The diodes (Al/polymer–nanotube com-posite/ITO) with low nanotube concentration (1%) show photovoltaic behavior, with an open circuit voltage of 0.75 V. The short circuit current is increased by two orders of magnitude compared with the pristine polymer diodes and the fill factor (ff) also increases from 0.3 to 0.4 for the nanotube–polymer cells. It is proposed that the photovoltaic response of these devices is based on the introduction of internal polymer–nanotube junctions within the polymer matrix, which due to a photoinduced electron transfer from the polymer to the nanotube contribute to enhanced charge separation and collection.