Electric field created p-n junction in composite films made from carbon nanotubes, iron (III) sulfate and polyvinyl alcohol.

Suspension made of Fe2(SO4)3(aq), polyvinyl alcohol and carbon nanotubes is placed in electric field to separate charges. Charges remain separated as suspension solidifies, forming composite films with cations and anions enriched at opposite sides. Polarized films behave as junction diodes with forward current and threshold voltage found to be 10-4-10-5 A and 2.4-2.6 V at ± 5 V. Rectification is preserved in strained composite films.