An alkoxy-substituted poIy(phenyIene thiophene) is used in order to suspend single-walled carbon nanotubes in an organic solvent. The suspension is spread on the air-water interface of a Langmuir trough and the floating film is characterized by means of Brewster angle microscopy and UV-visible reflection spectroscopy and the compression isotherm is recorded. The polymer/carbon- nanotube blend is transferred onto different substrates using the Langmuir-Blodgett technique. AFM measurements indicate the formation of globular structures for the samples transferred at low surfacepressure values and a tubular morphology for high-pressure-deposited samples. AFM analysis is repeated on a sample exposed to soft X-rays for about S h and a highly organized structure of bundles of carbon nanotubes rises up. Samples with different numbers of layers are transferred onto ITO substrates by means of the Langmuir-Blodgett method and are tested as photocathodes in a photo-electrochemical cell. A Voc of 0.18 V, an Isc of 85.8 mA, FF of 40.0%, and β of (6.23 × 10-3)% are obtained.