  A boost in the development of flexible and wearable electronics facilitates
the design of new materials to be applied as transparent conducting films
(TCFs). Although single-walled carbon nanotube (SWCNT) films are the most
promising candidates for flexible TCFs, they still do not meet optoelectronic
requirements demanded their successful industrial integration. In this study,
we proposed and thoroughly investigated a new approach that comprises
simultaneous bilateral (outer and inner surfaces) SWCNT doping after their
opening by thermal treatment at 400 C under an ambient air atmosphere. Doping
by a chloroauric acid (HAuCl$_{4}$) ethanol solution allowed us to achieve the
record value of sheet resistance of 31 $\pm$ 4 $\Omega$/sq at a transmittance
of 90% in the middle of visible spectra (550 nm). The strong p-doping was
examined by open-circuit potential (OCP) measurements and confirmed by ab
initio calculations demonstrating a downshift of Fermi level around 1 eV for
the case of bilateral doping.

Materials Science;Applied Physics;Computational Physics