Solvent effects on the electrical and optical properties of composite carbon nanotube/MEH-PPV films

Abstract

Optical signals were used to modulate the resistance of single-walled carbon nanotube–polymer composite films for development of optical switching devices. Films were fabricated from nanotubes dispersed in poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) solutions in either tetrahydrofuran (THF) or toluene. MEH-PPV was affected by the solvent choice, with THF causing an absorbance shift to shorter wavelengths. Composite films formed from THF dispersions showed 1–4% resistance decreases when illuminated with a green diode laser. Illumination of toluene-based films showed up to 5.4% resistance decreases, smaller than expected based on the polymer solution absorbance. Fluorescent emission from the polymer in toluene appears to inhibit charge transfer from the polymer to the nanotubes. THF films were unaffected by illumination with a red diode laser, while toluene dispersion films showed resistance decreases up to 1%. Nanotube dispersion and film formation reproducibility, evaluated for both the solvents, showed that the solvent affected film resistance and dispersion stability.