Bridging the Junction: Electrical Conductivity of Carbon Nanotube Networks

Carbon nanotube (CNT) films have excellent conductivity and suitable flexibility for chemical sensing and touch screen devices. Understanding the pathways of charge transport within the network is crucial to develop new functional materials and improve existing devices. Here, we study the electrical conductivity of networks of CNTs containing Group 11 metals (Au, Ag, and Cu), s-p metals (K, Ca, and Al), AuCl3, AuCl4, and Cl using quantum mechanical methods and semiclassical Boltzmann transport theory. The conductivity is characterized along the nanotubes and across the intersecting junction. The conductivity is much weaker across the junction than along the nanotubes and could be strengthened in all directions using dopants. The largest increase in conductivity is induced by Al along the nanotubes and by Cu across the intersection [389-fold and 14-fold relative to the pristine (8,0) network, respectively]. Additionally, Ag dopants activate charge transport along the semiconducting nanotube in heterogeneous networks of mixed metal and semiconducting nanotubes. The conductivity along the semiconducting nanotube increased 781-fold. This activation removes the bottleneck of charge transport along the semiconducting nanotubes within the network of mixed chiralities. Small amounts of dopants within nanotube networks drastically change the directional conductivity and provide new pathways for charge transport for applications such as chemical sensing or touch screens.

Automated summary

Carbon nanotube films have excellent conductivity and flexibility for chemical sensing and touch screen devices. Understanding how charge is transported within the network is crucial for developing new materials and improving existing devices. In this study, the conductivity of networks of carbon nanotubes containing different metals and dopants was investigated using quantum mechanical methods. The results showed that the conductivity along the nanotubes is stronger than across the junction, and dopants can enhance the conductivity in all directions. Adding aluminum increased the conductivity along the nanotubes by 389 times, while adding copper increased the conductivity across the junction by 14 times. Additionally, adding silver dopants activated charge transport along the semiconducting nanotubes, increasing the conductivity by 781 times. These findings have implications for applications such as chemical sensing and touch screens.