Stable Doping of Carbon Nanotubes via Molecular Self Assembly

We report a novel method for stable doping of carbon nanotubes (CNT) based on methods of molecular self assembly. A conformal growth of a self-assembled monolayer of fluoroalkyl tri-chloro-silane (FTS) at CNT surfaces results in a strong increase of the sheet conductivity of CNT electrodes by 60-300%, depending on the CNT chirality and composition. The charge carrier mobility of undoped partially aligned CNT films was independently estimated in a field-effect transistor geometry (~100 cm² V⁻¹ s⁻¹). The hole density induced by the FTS monolayer in CNT sheets is estimated to be similar to 1.8 x 10¹⁴ cm⁻². We also show that FTS doping of CNT anodes greatly improves the performance of organic solar cells. This large and stable doping effect, easily achieved in large area samples, makes this approach very attractive for applications of CNTs in transparent and flexible electronics.