Brightening of excitons in carbon nanotubes on dimensionality modification

Despite the attractive one-dimensional characteristics of carbon nanotubes 1 , their typically low luminescence quantum yield, restricted because of their one-dimensional nature 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , has limited the performance of nanotube-based light-emitting devices 10 , 11 . Here, we report the striking brightening of excitons (bound electron–hole pairs) 12 , 13 in carbon nanotubes through an artificial modification of their effective dimensionality from one dimension to zero dimensions. Exciton dynamics in carbon nanotubes with luminescent, local zero-dimension-like states generated by oxygen doping 14 were studied as model systems. We found that the luminescence quantum yield of the excitons confined in the zero-dimension-like states can be more than at least one order larger (∼18%) than that of the intrinsic one-dimensional excitons (typically ∼1%), not only because of the reduced non-radiative decay pathways but also due to an enhanced radiative recombination probability beyond that of intrinsic one-dimensional excitons. Our findings are extendable to the realization of future nanoscale photonic devices including a near-infrared single-photon emitter operable at room temperature. Artificially reducing the effective dimensionality of carbon nanotubes from one to zero dimensions increases the luminescence quantum yield of excitons confined in zero-dimensional-like states to ∼18%, which is over one order of magnitude larger than that of intrinsic one-dimensional excitons (∼1%). This finding will help realize future nanoscale photonic devices.