Tuning Carbon Nanotubes for Application in Solar Cells
Abstract
We achieved the control of diameter, length and level of nitrogen doping in synthesis of nitrogen doped carbon nanotubes (N-CNTs) through careful selection of catalyst, precursor mixture, and chemical vapor deposition (CVD) synthesis temperature. Solutions of butanol and acetonitrile (20% acetonitrile) were pyrolysed over a Fe/Al/MgO catalyst in a CVD reactor at temperatures from 700 oC to 1000 oC. The products were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and Raman spectroscopy. NCNTs with well graphitized morphology, small diameter, and narrow diameter distribution were obtained at CVD temperatures from 850 oC to 950 oC. Below 800 oC N-CNTs with large sized diameters were formed and above 950 oC the product yield became very low, and the carbon nanotubes were malformed with wide diameter distributions. By pyrolysing precursor mixtures of acetonitrile and alcohols (methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol and octanol) we found out that short, 500 nm in length, N-CNTs were obtained by the pyrolysis of long chain alcohols, (heptanol and octanol) and acetonitrile solution whilst longer N-CNTs were formed from pyrolysis of shorter chain alcohols (methanol, ethanol and propanol).