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Abstract

Narrowband photoluminescence (PL) in the near-infrared and electrical exciton generation make semiconducting single-walled carbon nanotubes (SWNTs) promising materials for optoelectronic devices. The functionalization of SWNTs with luminescent sp3 defects offers synthetically tunable light emission and enhances their potential for applications such as quantum light sources, bioimaging and sensing. However, the synthetic protocols that are currently used to create these defects are limited to aqueous dispersions of SWNTs, which are compromised by short tube lengths, residual metallic SWNTs and poor solution-processability. Here, the combination of highly selective polymer-sorting and shear force mixing as a mild exfoliation method provides electronically-pure (6,5) SWNTs in toluene with average tube lengths > 1 µm and strategies for their sp3 functionalization are developed based on simple diazonium chemistry. The complexation by an ether crown allows for the solubilization of commercially available aryldiazonium salts in organic solvents and thus enables their reaction with polymer-wrapped SWNTs. The resulting defect-tailored (6,5) SWNTs show a relatively high photoluminescence quantum yield (PLQY) of up to 4 % with 90 % of photons emitted from the sp3 defect. The dependence of the defect-induced PL brightening on the nanotube length indicates that the PLQY of the pristine SWNT may exceed that of the sp3 defect for a sufficiently high nanotube quality. By using custom-synthesized diazonium salts in a modified protocol, stable organic radicals are covalently attached to purified semiconducting SWNTs via luminescent aryl defects. The proximity between the defect-localized exciton and the unpaired electron promotes spin exchange and electron transfer processes, which are identified through time-resolved PL measurements. The results point toward an increased yield of triplet excitons due to radical-enhanced intersystem crossing, which could serve as a general concept to probe triplet states in SWNTs. The dispersion in organic solvents facilitates the integration of defect-tailored, polymer-wrapped SWNTs into optoelectronic devices. A planar dielectric waveguide structure channels the PL emitted from sp3 defects over distances > 1 mm and thus represents a first step toward their interfacing with photonic circuits and photovoltaic devices. Moreover, the demonstration of electroluminescence from sp3 defects in light-emitting field-effect transistors underpins their potential for electrically-driven single-photon sources.