Arresting Photodegradation in Semiconducting Single-Walled\nCarbon Nanotube Thin Films

Abstract

Solid-state dispersions\nof isolated single-walled carbon nanotubes\n(SWCNTs) in polymer matrices or networks of electronically coupled\nSWCNTs are gaining interest for a broad variety of optoelectronic\napplications. However, little is known about either the stability\nor degradation mechanisms of these systems. We show dramatic sp²-to-sp³ defect transformations of the SWCNT sidewall\nwhen either the S₁₁ or S₂₂ exciton transitions\nare optically pumped in ambient conditions, leading to the rapid decay\nof absorption and emission properties in less than 24 h for conditions\nsimilar to exposure to solar illumination. Importantly, we demonstrate\nthat either (i) encapsulation to block reactive O₂ from\nSWCNT excited states or (ii) exciton quenching via donor-to-acceptor\nelectron transfer is an effective route for “kinetic stabilization”\nagainst photodegradation, with <8% loss in absorbance after 1200\nh of illumination. We find that SWCNT:polymer loading does not impact\ndegradation. Our study suggests that the sp³ defects are\nassociated with the formation of oxygenic groups on the SWCNT sidewall.\nWhile such defect populations can detrimentally evolve over time in\nfilms where SWCNTs are environmentally exposed in the presence of\nlight, we offer multiple pathways to arrest this degradation and enable\ntheir robust application as advanced optical materials in optical\nand electronic devices.