Ultrafast exciton trapping dynamics in oxygen-functionalized single-walled carbon nanotubes

Abstract

Artificial zero-dimensional quantum defects within single-walled carbon nanotubes hold immense promise for diverse optoelectronic applications such as bioimaging, near-infrared light emission, nanolasing, and single-photon generation. This study delves into the temporal behavior of excitons within oxygen-functionalized single-walled carbon nanotubes, employing ultrafast transient absorption spectroscopy. Our investigation unveils the emergence of functionalization-induced excitonic states, distinguished by a long-lasting induced transmittance signal. Remarkably, even at low degree of functionalization, we observe a reduction in the lifetime of band-edge excitons. In contrast, the population dynamics of deep-band excitons exhibit resilience against low and moderate functionalization degrees, with a pronounced reduction manifesting only at high degrees of functionalization. Our findings align closely with a kinetic model that accounts for an additional relaxation channel prompted by functionalization. This empirical evidence provides a significant breakthrough, establishing that the formation of functionalization-induced excitonic states within oxygen-functionalized single-walled carbon nanotubes is a consequence of the diffusive trapping of free band edge excitons, while interaction of deep band excitons with oxygen defect sites rather yields in exciton recombination. These insights shed light on the intricate dynamics of excitons within single-walled carbon nanotube with artificially embedded quantum defects, advancing our understanding and potential applications in the realm of optoelectronics.