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Ultrafast exciton transport at early times in quantum dot solids


Quantum dot (QD) solids are an emerging platform for developing a range of optoelectronic devices. Thus, understanding exciton dynamics is essential towards developing and optimizing QD devices. Here, using transient absorption microscopy, we reveal the initial exciton dynamics in QDs with femtosecond timescales. We observe high exciton diffusivity (~102 cm2 s–1) in lead chalcogenide QDs within the first few hundred femtoseconds after photoexcitation followed by a transition to a slower regime (~10–1–1 cm2 s–1). QD solids with larger interdot distances exhibit higher initial diffusivity and a delayed transition to the slower regime, while higher QD packing density and heterogeneity accelerate this transition. The fast transport regime occurs only in materials with exciton Bohr radii much larger than the QD sizes, suggesting the transport of delocalized excitons in this regime and a transition to slower transport governed by exciton localization. These findings suggest routes to control the optoelectronic properties of QD solids.

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Fig. 1: The fs-TAM measurement of QD thin films with different capping ligands.
Fig. 2: Quantitative fs-TAM measurement results of the series of QD thin films.
Fig. 3: Quality and structural information of the QDs and films with different ligands and correlation to the fs-TAM results.
Fig. 4: The fs-TAM measurement results of other QD materials and schematics of exciton delocalization in QD solids.

Data availability

The data underlying all figures in this article are publicly available from the University of Cambridge repository at


  1. Lee, J. S., Kovalenko, M. V., Huang, J., Chung, D. S. & Talapin, D. V. Band-like transport, high electron mobility and high photoconductivity in all-inorganic nanocrystal arrays. Nat. Nanotechnol. 6, 348–352 (2011).

    Article  CAS  Google Scholar 

  2. Sun, L. et al. Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control. Nat. Nanotechnol. 7, 369–373 (2012).

    Article  CAS  Google Scholar 

  3. Liu, M. et al. Hybrid organic–inorganic inks flatten the energy landscape in colloidal quantum dot solids. Nat. Mater. 16, 258–263 (2017).

    Article  CAS  Google Scholar 

  4. Chuang, C. H., Brown, P. R., Bulovic, V. & Bawendi, M. G. Improved performance and stability in quantum dot solar cells through band alignment engineering. Nat. Mater. 13, 796–801 (2014).

    Article  CAS  Google Scholar 

  5. Lan, X. et al. Quantum dot solids showing state-resolved band-like transport. Nat. Mater. 19, 323–329 (2020).

    Article  CAS  Google Scholar 

  6. Kagan, C. R., Lifshitz, E., Sargent, E. H. & Talapin, D. V. Building devices from colloidal quantum dots. Science 353, aac5523 (2016).

    Article  CAS  Google Scholar 

  7. Kagan, C. R. & Murray, C. B. Charge transport in strongly coupled quantum dot solids. Nat. Nanotechnol. 10, 1013–1026 (2015).

    Article  CAS  Google Scholar 

  8. Crisp, R. W., Schrauben, J. N., Beard, M. C., Luther, J. M. & Johnson, J. C. Coherent exciton delocalization in strongly coupled quantum dot arrays. Nano Lett. 13, 4862–4869 (2013).

    Article  CAS  Google Scholar 

  9. Choi, J. H. et al. Bandlike transport in strongly coupled and doped quantum dot solids: a route to high-performance thin-film electronics. Nano Lett. 12, 2631–2638 (2012).

    Article  CAS  Google Scholar 

  10. Akselrod, G. M. et al. Visualization of exciton transport in ordered and disordered molecular solids. Nat. Commun. 5, 3646 (2014).

    Article  CAS  Google Scholar 

  11. Akselrod, G. M. et al. Subdiffusive exciton transport in quantum dot solids. Nano Lett. 14, 3556–3562 (2014).

    Article  CAS  Google Scholar 

  12. Zhu, T., Wan, Y., Guo, Z., Johnson, J. & Huang, L. Two birds with one stone: tailoring singlet fission for both triplet yield and exciton diffusion length. Adv. Mater. 28, 7539–7547 (2016).

    Article  CAS  Google Scholar 

  13. Yoon, S. J., Guo, Z., Dos Santos Claro, P. C., Shevchenko, E. V. & Huang, L. Direct imaging of long-range exciton transport in quantum dot superlattices by ultrafast microscopy. ACS Nano 10, 7208–7215 (2016).

    Article  CAS  Google Scholar 

  14. Ginsberg, N. S. & Tisdale, W. A. Spatially resolved photogenerated exciton and charge transport in emerging semiconductors. Annu. Rev. Phys. Chem. 71, 1–30 (2020).

    Article  CAS  Google Scholar 

  15. Delor, M., Weaver, H. L., Yu, Q. & Ginsberg, N. S. Imaging material functionality through three-dimensional nanoscale tracking of energy flow. Nat. Mater. 19, 56–62 (2020).

    Article  CAS  Google Scholar 

  16. Sung, J. et al. Long-range ballistic propagation of carriers in methylammonium lead iodide perovskite thin films. Nat. Phys. 16, 171–176 (2019).

    Article  CAS  Google Scholar 

  17. Guo, Z., Manser, J. S., Wan, Y., Kamat, P. V. & Huang, L. Spatial and temporal imaging of long-range charge transport in perovskite thin films by ultrafast microscopy. Nat. Commun. 6, 7471 (2015).

    Article  CAS  Google Scholar 

  18. Choi, J. J. et al. Photogenerated exciton dissociation in highly coupled lead salt nanocrystal assemblies. Nano Lett. 10, 1805–1811 (2010).

    Article  CAS  Google Scholar 

  19. Schnedermann, C. et al. Ultrafast tracking of exciton and charge carrier transport in optoelectronic materials on the nanometer scale. J. Phys. Chem. Lett. 10, 6727–6733 (2019).

    Article  CAS  Google Scholar 

  20. Zhang, J. et al. Carrier transport in PbS and PbSe QD films measured by photoluminescence quenching. J. Phys. Chem. C 118, 16228–16235 (2014).

    Article  CAS  Google Scholar 

  21. Weidman, M. C., Yager, K. G. & Tisdale, W. A. Interparticle spacing and structural ordering in superlattice PbS nanocrystal solids undergoing ligand exchange. Chem. Mater. 27, 474–482 (2014).

    Article  CAS  Google Scholar 

  22. Contreras-Pulido, L. D. & Bruderer, M. Coherent and incoherent charge transport in linear triple quantum dots. J. Phys. Condens. Matter 29, 185301 (2017).

    Article  CAS  Google Scholar 

  23. Barford, W. & Duffy, C. D. P. Role of quantum coherence and energetic disorder in exciton transport in polymer films. Phys. Rev. B 74, 075207 (2006).

    Article  CAS  Google Scholar 

  24. Cohen, E. et al. Achieving exciton delocalization in quantum dot aggregates using organic linker molecules. J. Phys. Chem. Lett. 8, 1014–1018 (2017).

    Article  CAS  Google Scholar 

  25. Geiregat, P., Justo, Y., Abe, S., Flamee, S. & Hens, Z. Giant and broad-band absorption enhancement in colloidal quantum dot monolayers through dipolar coupling. ACS Nano 7, 987–993 (2013).

    Article  CAS  Google Scholar 

  26. Kagan, C. R., Murray, C. B., Nirmal, M. & Bawendi, M. G. Electronic energy transfer in CdSe quantum dot solids. Phys. Rev. Lett. 76, 1517–1520 (1996).

    Article  CAS  Google Scholar 

  27. He, S. et al. Engineering sensitized photon upconversion efficiency via nanocrystal wavefunction and molecular geometry. Angew. Chem. Int. Ed. 59, 17726–17731 (2020).

    Article  CAS  Google Scholar 

  28. Koole, R., Liljeroth, P., de Mello Donega, C., Vanmaekelbergh, D. & Meijerink, A. Electronic coupling and exciton energy transfer in CdTe quantum-dot molecules. J. Am. Chem. Soc. 128, 10436–10441 (2006).

    Article  CAS  Google Scholar 

  29. Ma, W., Luther, J. M., Zheng, H., Wu, Y. & Alivisatos, A. P. Photovoltaic devices employing ternary PbSxSe1-x nanocrystals. Nano Lett. 9, 1699–1703 (2009).

    Article  CAS  Google Scholar 

  30. Collini, E. et al. Room-temperature inter-dot coherent dynamics in multilayer quantum dot materials. J. Phys. Chem. C 124, 16222–16231 (2020).

    Article  CAS  Google Scholar 

  31. Razgoniaeva, N. et al. One-dimensional carrier confinement in “giant” CdS/CdSe excitonic nanoshells. J. Am. Chem. Soc. 139, 7815–7822 (2017).

    Article  CAS  Google Scholar 

  32. Jethi, L., Mack, T. G. & Kambhampati, P. Extending semiconductor nanocrystals from the quantum dot regime to the molecular cluster regime. J. Phys. Chem. C 121, 26102–26107 (2017).

    Article  CAS  Google Scholar 

  33. Protesescu, L. et al. Nanocrystals of cesium lead halide perovskites (CsPbX3, X = Cl, Br, and I): novel optoelectronic materials showing bright emission with wide color gamut. Nano Lett. 15, 3692–3696 (2015).

    CAS  Google Scholar 

  34. Wise, F. W. Lead salt quantum dots: the limit of strong quantum confinement. Acc. Chem. Res. 33, 773–780 (2000).

    Article  CAS  Google Scholar 

  35. Lee, E. M. Y., Tisdale, W. A. & Willard, A. P. Perspective: nonequilibrium dynamics of localized and delocalized excitons in colloidal quantum dot solids. J. Vac. Sci. Technol. A 36, 068501 (2018).

    Article  CAS  Google Scholar 

  36. Sharma, A. et al. Supertransport of excitons in atomically thin organic semiconductors at the 2D quantum limit. Light Sci. Appl. 9, 116 (2020).

    Article  CAS  Google Scholar 

  37. Fratini, S., Nikolka, M., Salleo, A., Schweicher, G. & Sirringhaus, H. Charge transport in high-mobility conjugated polymers and molecular semiconductors. Nat. Mater. 19, 491–502 (2020).

    Article  CAS  Google Scholar 

  38. Schweicher, G. et al. Chasing the “killer” phonon mode for the rational design of low-disorder, high-mobility molecular semiconductors. Adv. Mater. 31, 1902407 (2019).

    Article  CAS  Google Scholar 

  39. Hines, M. A. & Scholes, G. D. Colloidal PbS nanocrystals with size-tunable near-infrared emission: observation of post-synthesis self-narrowing of the particle size distribution. Adv. Mater. 15, 1844–1849 (2003).

    Article  CAS  Google Scholar 

  40. Nienhaus, L. et al. Speed limit for triplet-exciton transfer in solid-state PbS nanocrystal-sensitized photon upconversion. ACS Nano 11, 7848–7857 (2017).

    Article  CAS  Google Scholar 

  41. de Mello, J. C., Wittmann, H. F. & Friend, R. H. An improved experimental determination of external photoluminescence quantum efficiency. Adv. Mater. 9, 230–232 (1997).

    Article  Google Scholar 

  42. Jiang, Z. GIXSGUI: a MATLAB toolbox for grazing-incidence X-ray scattering data visualization and reduction, and indexing of buried three-dimensional periodic nanostructured films. J. Appl. Crystallogr. 48, 917–926 (2015).

    Article  CAS  Google Scholar 

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This work has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 758826). Z.Z. acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Actions grant (no. 842271, TRITON project). J.S. acknowledges support from the DGIST Start-up Fund Program of the Ministry of Science and ICT (2022010005). We acknowledge support from the Engineering and Physical Sciences Research Council (UK) via grants EP/P027741/1, EP/P027814/1 and EP/M006360/1. We thank D. Paleček and C. Schnedermann (University of Cambridge) for the assistance with the TA spectroscopy measurements and for the useful discussion on transport dynamics. We also thank Y. Wu (A*STAR Singapore) for the support on figure preparations.

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Authors and Affiliations



Z.Z., J.S. and A.R. conceived the project. Z.Z. performed the sample synthesis and fabrication. Z.Z. and J.S. performed fs-TAM and other optical measurements. R.P. performed measurements on cadmium chalcogenide QD solids. D.T.W.T., M.P.W., A.J.R. and R.A.L.J. supported and performed the GISAXS measurements and analysis. S. Han and M.L. provided input into the sample preparation. J.X. conducted electron microscopy measurements. S.D. contributed to the PLQY measurements. S. Huang provided input into the design of the experiments and discussion of results. Z.Z., J.S. and A.R. wrote the paper with input from all authors.

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Correspondence to Jooyoung Sung or Akshay Rao.

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Supplementary Figs. 1–37, Tables 1–4, Discussion and experimental details.

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Zhang, Z., Sung, J., Toolan, D.T.W. et al. Ultrafast exciton transport at early times in quantum dot solids. Nat. Mater. 21, 533–539 (2022).

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