Tunable room-temperature single-photon emission at telecom wavelengths from sp3 defects in carbon nanotubes

Journal name:
Nature Photonics
Year published:
Published online


Generating quantum light emitters that operate at room temperature and at telecom wavelengths remains a significant materials challenge. To achieve this goal requires light sources that emit in the near-infrared wavelength region and that, ideally, are tunable to allow desired output wavelengths to be accessed in a controllable manner. Here, we show that exciton localization at covalently introduced aryl sp3 defect sites in single-walled carbon nanotubes provides a route to room-temperature single-photon emission with ultrahigh single-photon purity (99%) and enhanced emission stability approaching the shot-noise limit. Moreover, we demonstrate that the inherent optical tunability of single-walled carbon nanotubes, present in their structural diversity, allows us to generate room-temperature single-photon emission spanning the entire telecom band. Single-photon emission deep into the centre of the telecom C band (1.55 µm) is achieved at the largest nanotube diameters we explore (0.936 nm).

At a glance


  1. Illustration of exciton localization and wavelength-tunable defect-state emission (E11* and E11*−) in aryl-functionalized SWCNTs of varying (n,m).
    Figure 1: Illustration of exciton localization and wavelength-tunable defect-state emission (E11* and E11*) in aryl-functionalized SWCNTs of varying (n,m).

    a, The (6,5), (7,5) and (10,3) structural series represents a SWCNT progression to larger diameter, each functionalized with a single covalently bound aryl defect site. Band diagrams of the aryl-functionalized (n,m) series show standard E11 exciton emission energies decreasing as diameter increases. The sp3 defects create deep-trap states (E11* and E11*, the latter not shown) below the original E11, in which optically generated excitons are trapped and can relax to the ground state to emit a single photon. The decrease in E11* energies parallels that for E11 as diameter increases, thus allowing defect-state emission wavelengths to be tuned to telecom wavelengths. For clarity, the lower energy defect-state emission band (E11*) has been omitted from the energy diagrams. Similar to E11*, this band also decreases in energy as nanotube diameter is increased. b, Example defect-state spectra obtained from (6,5) (top), (7,5), middle and (10,3) (bottom) structures. Each individual spectrum is obtained from a single nanotube at room temperature using identical excitation and collection conditions. Variability in spectral intensities illustrates natural tube-to-tube differences. Heterogeneity in the environment experienced by individual defect sites at the single tube level and the possibility of multiple binding configurations on the nanotube lattice29 (resulting in the E11* and E11* emission bands, Supplementary Fig. 1a) probably results in the range of emission wavelengths observed here in the single-nanotube spectra for the same dopant (additional Cl2-Dz and MeO-Dz examples are presented in the Supplementary Materials and ensemble spectra in Supplementary Fig. 1a). Positions of the two defect-state photoluminescence bands (E11* and E11*) appearing in ensemble spectra (Supplementary Fig. 1a) are noted as reference points by dotted lines. Note that the sum of spectra from individual nanotubes of a given bulk sample mimics the observed solution-phase ensemble spectrum for that sample (Supplementary Fig. 1b).

  2. Photoluminescence characteristics and photon antibunching properties of sp3 defect-state emission (E11* and E11*−) from aryl-functionalized (6,5), (7,5) and (10,3) SWCNTs.
    Figure 2: Photoluminescence characteristics and photon antibunching properties of sp3 defect-state emission (E11* and E11*) from aryl-functionalized (6,5), (7,5) and (10,3) SWCNTs.

    al, Behaviours for (6,5) SWCNTs in PFO-bpy (ad), (7,5) SWCNTs in DOC (eh) and (10,3) SWCNTs in DOC (il) encapsulation, deposited on polystyrene-coated substrates and functionalized with Cl2-Dz or MeO-Dz. Photoluminescence spectra (a,e,i), second-order photon correlation (g(2)) plots (b,f,j), time traces (100 ms per time point) with corresponding σQE/σSN values (c,g,k) and photoluminescence decay curves (d,h,l). All data are for single tubes, with (6,5) and (7,5) data obtained at 298 K and (10,3) data obtained at 220 K. The likely band origin of the defect-state emission is labelled, based on relative position with respect to the E11* and E11* positions shown in Fig. 1b. Time traces include count rate histograms (c,g,k, right inset, black trace) and are fit to a Gaussian distribution (right inset, red trace). Photoluminescence decay curves are fit to a bi-exponential function (black), with lifetime components indicated. The instrument response function, in relation to experimental decays, is shown in Supplementary Fig. 5c.

  3. Global trends in single-photon emission statistics and dynamics over the complete range of SWCNT (n,m) and observed E11* emission wavelengths.
    Figure 3: Global trends in single-photon emission statistics and dynamics over the complete range of SWCNT (n,m) and observed E11* emission wavelengths.

    a, Probabilities of observing single-photon emission with g2(0) ≤ 0.1 and g2(0) ≤ 0.05 for chiralities (6,5), (7,5) and (10,3), each based on a total of 30 individual nanotubes, with each displaying a single defect-state emission peak. b, Example g2(0) values (black, lower) ≤0.05 observed at different wavelength and corresponding σQE/σSN values (blue, top) evaluated for (6,5), (7,5) and (10,3) SWCNTs. Values of 0.01 are noise-limited. c, Observed average photoluminescence lifetimes for four sample types observed across the photoluminescence wavelength range. Data are combined results for both Cl2-Dz and MeO-Dz functionalization and span both E11* and E11* emission bands. Error bars are obtained as fitting errors from the bi-exponential fits of the photoluminescence decay curves.


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Author information


  1. Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

    • Xiaowei He,
    • Nicolai F. Hartmann,
    • Xuedan Ma,
    • Younghee Kim,
    • Han Htoon &
    • Stephen K. Doorn
  2. Chemical and Materials Science Center, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401, USA

    • Rachelle Ihly &
    • Jeffrey L. Blackburn
  3. Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, USA

    • Weilu Gao &
    • Junichiro Kono
  4. Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0372, Japan

    • Yohei Yomogida
  5. Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan

    • Atsushi Hirano,
    • Takeshi Tanaka &
    • Hiromichi Kataura


H.H. and S.K.D. conceived and designed the experiment. X.H., under the supervision of H.H. and S.K.D. and with assistance from X.M. and Y.K., performed all spectroscopy studies and data analysis and, with N.F.H. under the supervision of S.K.D., performed nanotube separation and functionalization. R.I. and J.L.B. provided PFO-bpy-wrapped (6,5) SWCNT material. Y.Y., A.H., T.T., H.K., W.G. and J.K. provided (10,3) SWCNT material. X.H., H.H. and S.K.D. prepared the manuscript with assistance from all other co-authors.

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