Enhancing Optoelectronic Performance of Randomly Oriented Single-Walled Carbon Nanotube Films

Abstract

Randomly oriented single-walled carbon nanotubes (SWCNTs) in the form of films are a promising material for various optoelectronic and photonic applications, including actual flexible and stretchable, transparent and conductive electrodes. However, the optoelectronic performance of as-synthesized SWCNT films still needs to be improved in order to provide industry-required conductivity characteristics. In this thesis, several novel approaches are introduced to enhance the optoelectronic properties of the films by an adsorption doping technique. The first approach based on the creation of a hybrid graphene/SWCNT material allowed us to reduce the sheet resistance by introducing a large area π-stacking interaction between the carbon nanomaterials. The second one is devoted to the optimization of an adsorption doping technique with a correct selection of a dopant solvent in which the evaporation rate is the most important parameter to control the optoelectric properties of the SWCNT films. The final one presents an aerosol-assisted approach that focuses on a uniform, controllable, and reproducible doping which leads to fine-tuning of the SWCNT film work function and conductivity. Additionally, the optical properties of the as-synthesized and doped nanotubes were extensively studied using broad wavelength non-destructive spectroscopies and optical pumping with a terahertz probe. The first study contributes and confirms the observable spectral effects for free carriers described in the Drude conductivity model. The second one identifies strong negative photoconductivity in both pristine and doped nanotubes. As a result, each of these cases leads to the creation of the SWCNT films that exhibit superior properties. This opens up numerous breathtaking opportunities for today and upcoming devices.