Semiconducting Single‐Walled Carbon Nanotubes or Very Rigid Conjugated Polymers: A Comparison

Abstract

With the ability to produce large amounts of purely semiconducting and even monochiral dispersions of single-walled carbon nanotubes (SWCNT) their application as a bulk material in thin film devices on a large scale becomes feasible. Their physical properties, processing, and final devices are quite similar to those of semiconducting polymers. In the extreme case one may view carbon nanotubes as very long, rigid, and fully conjugated polymers. This analogy raises the question whether the knowledge accumulated over the last two decades of processing and studying conjugated polymers could be transferred to solution-processed nanotube devices. Here, the optical and electronic properties of both materials in solution and in thin films are discussed and compared with a focus on their application in optoelectronic devices. Some striking similarities and common issues are highlighted to show the connection between conjugated polymers and SWCNTs as 1D semiconductors.

Charge transport physics of a unique class of rigid-rod conjugated polymers with fused-ring conjugated units linked by double carbon-carbon bonds

“…At these single-bond linkages, cis-trans isomerism or variations of the torsional angle between neighboring conjugated units can occur that limit π-electron delocalization and may change the orientation of the backbone. As a result, most conjugated polymers exhibit limited chain rigidity with random coil or worm-like conformations on length scales above 1 to 10 nm ( 12 ) and more flexibility compared with other π-conjugated systems such as carbon nanotubes ( 24 ). To date, the conjugated polymers with the longest persistence lengths have been found to be donor-acceptor copolymers with extended, fused-ring conjugated units linked by single bonds designed to exhibit steep torsion potentials ( 10 , 19 ).…”

Anisotropy of Charge Transport in a Uniaxially Aligned Fused Electron‐Deficient Polymer Processed by Solution Shear Coating

“…[ 26 ] Intuitively, it can be expected that this technique would be particularly favorable if the polymer has a rigid backbone structure allowing the realization of microstructures comparable to aligned carbon nanotube (CNT) networks. [ 30 ] Our fused polymer system should exhibit the ideal rigid backbone structure needed for polymer chain alignment and achieving a high degree of charge transport anisotropy that is expected to improve carrier mobilities along the chain alignment direction.…”

Recent Developments and Novel Applications of Thin Film, Light‐Emitting Transistors

“…However, the presence of residual metallic nanotubes and lack of control over the network composition (i.e., many nanotubes with different diameters and bandgaps) complicated the interpretation of these early nanotube thin film LEFETs. With the recent availability of very efficient sorting methods for nanotubes, for example, by density gradient ultracentrifugation, chromatography, two‐phase aqueous phase extraction and the simple and selective dispersion of SWCNTs by polymer wrapping, the fabrication of optoelectronic devices and specifically LEFETs based on purely semiconducting and monochiral SWCNTs became feasible and indeed very similar to device processing with semiconducting polymers …”