Investigating sulfur and selenium compounds as potential optically active defects on SWCNTs from first-principles theory

Semiconducting single-walled carbon nanotubes (SWCNT) containing sp3 dopants are promising optoelectronic materials due to their bright photoluminescence, long spin coherence, and exhibited single-photon emission. The presence of the defect causes a red-shifted photoemission, arising from the introduction of in-gap electronic states associated with the defect and symmetry breaking of the SWCNT bands. The magnitude of the red-shift is dependent on the defect introduced. We present a first-principles computational study of (6,5)-SWCNT functionalized with newly proposed sulfur and selenium-based compounds. First, we use density functional theory to investigate the likely product from the nanotube exposed to sodium dodecyl sulfate. Studying possible sulfate derivatives (S, SO, SO2, and SO3) we show that S and SO are the most likely defects obtained in experiment. In addition, many-body perturbation theory calculations within GW-BSE are used to investigate the optical properties of the tube containing S and Se atomic defects. We predict these defects result in low-energy optical transitions consistent with aryl functionalized tubes but show the potential to increase spin-orbit coupling, suggesting these functionalized tubes are candidates for use in in quantum-based technologies.