(Invited) Effects of Residual Wrapping Polymer on Charge and Exciton Transport in Semiconducting SWCNT Thin Films

The optical and electrical properties of single-walled carbon nanotubes (SWCNTs) make them attractive for a number of energy conversion devices, including thin-film photovoltaics and thermoelectrics. Both fundamental studies and device efficiencies have benefited from the ability to selectively extract semiconducting SWCNTs (s-SWCNTs) with high yield, purity, and throughput with pi-congujated semiconducting polymers such as polyfluorenes. However, it has proven to be challenging to quantitatively remove these polymers after selective extraction of s-SWCNTs, so thin films prepared from polyfluorene-based dispersions typically have significant amounts of residual polymer. Since charge and exciton transport within s-SWCNT thin films can be sensitive to the degree of inter-nanotube electronic coupling, the ultimate effects of this residual polymer on transport are unclear although they are likely to be deleterious. A number of polymers have recently emerged that can be decomposed into monomers after selective extraction of s-SWCNTs, enabling thin s-SWCNT film fabrication in the complete absence of residual wrapping polymer. In this presentation, I will discuss our recent results demonstrating large improvements to transport for films that are prepared with a removable polymer. These improvements translate directly into improved performance for a variety of thin-film devices based on s-SWCNTs.