Electronic transport on carbon nanotube networks: a multiscale computational approach

TL;DR

This paper presents a multiscale computational approach to analyze charge transport in disordered carbon nanotube networks, combining geometrical, resistivity, and ballistic transport calculations to understand and improve their conductivity.

Contribution

It introduces a combined macroscopic and microscopic modeling framework to evaluate transport properties and set upper bounds for conductivity in nanotube networks.

Findings

Network connectivity depends on nanotube concentration and aspect ratio.

Comparison with experiments helps estimate junction resistance.

Ballistic transport calculations provide an upper limit for conductivity.

Abstract

Carbon nanotube networks are one of the candidate materials to function as malleable, transparent, conducting films, with the technologically promising application of being used as flexible electronic displays. Nanotubes disorderly distributed in a film offers many possible paths for charge carriers to travel across the entire system, but the theoretical description of how this charge transport occurs is rather challenging for involving a combination of intrinsic nanotube properties with network morphology aspects. Here we attempt to describe the transport properties of such films in two different length scales. Firstly, from a purely macroscopic point of view we carry out a geometrical analysis that shows how the network connectivity depends on the nanotube concentration and on their respective aspect ratio. Once this is done, we are able to calculate the resistivity of a heavily disordered networked film. Comparison with experiment offers us a way to infer about the junction resistance between neighbouring nanotubes. Furthermore, in order to guide the frantic search for high-conductivity films of nanotube networks, we turn to the microscopic scale where we have developed a computationally efficient way for calculating the ballistic transport across these networks. While the ballistic transport is probably not capable of describing the observed transport properties of these films, it is undoubtedly useful in establishing an upper value for their conductivity. This can serve as a guideline in how much room there is for improving the conductivity of such networks.