Arresting Photodegradation in Semiconducting Single-Walled Carbon Nanotube Thin Films

Abstract

Solid-state dispersions of isolated single-walled carbon nanotubes (SWCNTs) in polymer matrices or networks of electronically coupled SWCNTs are gaining interest for a broad variety of optoelectronic applications. However, little is known about either the stability or degradation mechanisms of these systems. We show dramatic sp2-to-sp3 defect transformations of the SWCNT sidewall when either the S11 or S22 exciton transitions are optically pumped in ambient conditions, leading to the rapid decay of absorption and emission properties in less than 24 h for conditions similar to exposure to solar illumination. Importantly, we demonstrate that either (i) encapsulation to block reactive O2 from SWCNT excited states or (ii) exciton quenching via donor-to-acceptor electron transfer is an effective route for “kinetic stabilization” against photodegradation, with <8% loss in absorbance after 1200 h of illumination. We find that SWCNT:polymer loading does not impact degradation. Our study suggests that the sp3 defects are associated with the formation of oxygenic groups on the SWCNT sidewall. While such defect populations can detrimentally evolve over time in films where SWCNTs are environmentally exposed in the presence of light, we offer multiple pathways to arrest this degradation and enable their robust application as advanced optical materials in optical and electronic devices.