The goal of this project is to produce polymer-based solar cells using multiwalled carbon nanotubes (MWNTs) grown by chemical vapor deposition (CVD). Nanotubes were grown in a two-zone furnace using toluene solutions containing cyclopentadienyliron dicarbonyl dimer, which served as the nanotube catalyst source. The nanotubes were characterized by thermogravimetric analysis, Raman spectroscopy, high resolution transmission electron microscopy and scanning electron spectroscopy. Prototype solar cells were prepared with the top-down composition of Al/poly(3-octylthiophene)/MWNTs/indium tin oxide/polyethylene terephthalate. The polyethylene terephthalate substrate allows the solar cells to be flexible and lightweight. Detailed results will be presented. The work was supported by NASA Idaho Space Grant Consortium, NASA Idaho EPSCoR, NASA John H. Glenn Research Center, and the M.J. Murdock Charitable Trust.