Enhanced Electrical Performance and Stability of SWCNT Transparent Conductive Films via Dual Chemical Doping and Encapsulation

Transparent conductive films based on SWCNTs combine high transmittance, theoretical conductivity, and mechanical flexibility, offering a compelling alternative to brittle, infrared-limited indium tin oxide. However, the suboptimal optoelectronic performance of the SWCNT films caused by the presence of large intertube junction barriers as well as aggregated bundles hinders their application in optoelectronic devices. Herein, we demonstrate that these limits can be overcome by adopting a simple dual-doping and encapsulation strategy. We have proved that a low concentration of nitric acid is sufficient to realize effective p-doping on carbon nanotubes, thus avoiding the use of concentrated nitric acid in traditional processes. On this basis, we deliberately introduced ultrathin polyethylenimine and poly(methyl methacrylate) interlayers to reduce the work function and improve the stability of the SWCNT films, respectively. By adopting this strategy, the resulting SWCNT electrodes exhibit a low sheet resistance of ∼30 Ω sq^-1, high average infrared transparency of 87% and excellent air-stability. Owing to the balanced optical and electrical properties of transparent electrodes, as well as their tunable work function, highly sensitive photodetection is achieved in PbS colloidal quantum dot based short-wavelength infrared detectors, as demonstrated by the high external quantum efficiencies of 31% (n-i-p) and 42% (p-i-n) at 1550 nm, respectively. The mechanism and strategy described here provide insights into the design and optimization of high-performance SWCNT electrodes for next-generation optoelectronics.