Aligned Carbon Nanotube Thin Films from Liquid Crystal Polyelectrolyte Inks.
Single walled carbon nanotube thin films are fabricated by solution shearing from high concentration sodium nanotubide polyelectrolyte inks. The solutions are produced by simple stirring of the nanotubes with elemental sodium in dimethylacetamide, and the nanotubes are thus not subject to any sonication-induced damage. At such elevated concentrations (∼4 mg mL(-1)), the solutions exist in the liquid crystal phase and during deposition this order is transferred to the films, which are well aligned in the direction of shear with a 2D nematic order parameter of ∼0.7 determined by polarized absorption measurements. Compared to similarly formed films made from superacids, the polyelectrolyte films contain smaller bundles and a much narrower distribution of bundle diameters. After p-doping with an organic oxidizer, the films exhibit a very high DC electrical to optical conductivity ratio of σ(DC)/σ(OP) ∼ 35, corresponding to a calculated DC conductivity of over 7000 S cm(-1). When very thin (T550 ∼ 96%), smooth (RMS roughness, R(q) ∼ 2.2 nm), and highly aligned films made via this new route are used as the front electrodes of carbon nanotube-silicon solar cells, the power conversion efficiency is almost an order of magnitude greater than that obtained when using the much rougher (R(q) ∼ 20-30 nm) and less conductive (peak σ(DC)/σ(OP) ∼ 2.5) films formed by common vacuum filtration of the same starting material, and having the same transmittance.
Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT) , 76021 Karlsruhe, Germany.|Centre for Nanoscale Science and Technology (CNST), School of Chemical and Physical Sciences, Flinders University , Adelaide 5042, Australia.
Daniel D
DD
Tune
Chair for Photonics and Optoelectronics, Department of Physics and Center for Nanoscience (CeNS), Ludwig-Maximilians-Universität München , D-80799 München, Germany.
Adam J
AJ
Blanch
Centre for Nanoscale Science and Technology (CNST), School of Chemical and Physical Sciences, Flinders University , Adelaide 5042, Australia.
Cameron J
CJ
Shearer
Centre for Nanoscale Science and Technology (CNST), School of Chemical and Physical Sciences, Flinders University , Adelaide 5042, Australia.
Katherine E
KE
Moore
Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT) , 76021 Karlsruhe, Germany.
Moritz
M
Pfohl
Centre for Nanoscale Science and Technology (CNST), School of Chemical and Physical Sciences, Flinders University , Adelaide 5042, Australia.
Joseph G
JG
Shapter
Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT) , 76021 Karlsruhe, Germany.
Benjamin S
BS
Flavel
alignment; nematic; sodium nanotubide; solar cells; thin films