Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Heavy-atom engineering of thermally activated delayed fluorophores for high-performance X-ray imaging scintillators

Abstract

The architectural design and fabrication of low-cost and reliable organic X-ray imaging scintillators with high light yield, ultralow detection limits and excellent imaging resolution is becoming one of the most attractive research directions for chemists, materials scientists, physicists and engineers due to the devices’ promising scientific and applied technological implications. However, the optimal balance among X-ray absorption capability, exciton utilization efficiency and photoluminescence quantum yield of organic scintillation materials is extremely difficult to achieve because of several competitive non-radiative processes, including intersystem crossing and internal conversion. Here we introduced heavy atoms (Cl, Br and I) into thermally activated delayed fluorescence (TADF) chromophores to significantly increase their X-ray absorption cross-section and maintaining their unique TADF properties and high photoluminescence quantum yield. The X-ray imaging screens fabricated using TADF-Br chromophores exhibited highly improved X-ray sensitivity and imaging resolution compared with the TADF-H counterpart. More importantly, the high X-ray imaging resolution of >18.0 line pairs per millimetre achieved from the TADF-Br screen exceeds most reported organic and conventional inorganic scintillators. This study could help revive research on organic X-ray imaging scintillators and pave the way towards exciting applications for radiology and security screening.

This is a preview of subscription content, access via your institution

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Fig. 1: Illustration of the heavy-atom engineering strategy on the enhancement of X-ray sensitivity of TADF chromophores.
Fig. 2: Characterization of optical properties of TADF films.
Fig. 3: DFT calculations and TA spectroscopy measurements.
Fig. 4: RL and X-ray imaging applications.

Data availability

The main data supporting the findings of this study are available within this Article and its Supplementary Information. Further data are available from the corresponding author on reasonable request. Source data are provided with this paper.

References

  1. Chen, Q. et al. All-inorganic perovskite nanocrystal scintillators. Nature 561, 88–93 (2018).

    Article  ADS  Google Scholar 

  2. Yu, D. et al. Two-dimensional halide perovskite as β-ray scintillator for nuclear radiation monitoring. Nat. Commun. 11, 3395 (2020).

    Article  ADS  Google Scholar 

  3. Wu, H., Ge, Y., Niu, G. & Tang, J. Metal halide perovskites for X-ray detection and imaging. Matter 4, 144–163 (2021).

    Article  Google Scholar 

  4. Liang, S. et al. Recent advances in synthesis, properties, and applications of metal halide perovskite nanocrystals/polymer nanocomposites. Adv. Mater. 33, e2005888 (2021).

    Article  ADS  Google Scholar 

  5. Heo, J. H. et al. High-performance next-generation perovskite nanocrystal scintillator for nondestructive X-ray imaging. Adv. Mater. 31, e1801743 (2018).

    Article  ADS  Google Scholar 

  6. Clinckemalie, L. et al. Challenges and opportunities for CsPbBr3 perovskites in low- and high-energy radiation detection. ACS Energy Lett. 6, 1290–1314 (2021).

    Article  Google Scholar 

  7. Zhou, Y., Chen, J., Bakr, O. M. & Mohammed, O. F. Metal halide perovskites for X-ray imaging scintillators and detectors. ACS Energy Lett. 6, 739–768 (2021).

    Article  Google Scholar 

  8. Pan, W. et al. Cs2AgBiBr6 single-crystal X-ray detectors with a low detection limit. Nat. Photon. 11, 726–732 (2017).

    Article  ADS  Google Scholar 

  9. Wei, H. et al. Sensitive X-ray detectors made of methylammonium lead tribromide perovskite single crystals. Nat. Photon. 10, 333–339 (2016).

    Article  ADS  Google Scholar 

  10. Xu, L. J., Lin, X., He, Q., Worku, M. & Ma, B. Highly efficient eco-friendly X-ray scintillators based on an organic manganese halide. Nat. Commun. 11, 4329 (2020).

    Article  ADS  Google Scholar 

  11. Wei, J.-H. et al. All-inorganic lead-free heterometallic Cs4MnBi2Cl12 perovskite single crystal with highly efficient orange emission. Matter 3, 892–903 (2020).

    Article  Google Scholar 

  12. Jana, A., Park, S., Cho, S., Kim, H. & Im, H. Bounce back with triplet excitons for efficient X-ray scintillation. Matter 5, 20–22 (2022).

    Article  Google Scholar 

  13. Yang, B. et al. Lead-free halide Rb2CuBr3 as sensitive X-ray scintillator. Adv. Mater. 31, e1904711 (2019).

    Article  ADS  Google Scholar 

  14. Han, K. et al. Seed crystal induced cold sintering toward metal halide transparent ceramic scintillators. Adv. Mater. 34, e2110420 (2022).

    Article  ADS  Google Scholar 

  15. Ma, W. et al. Thermally activated delayed fluorescence (TADF) organic molecules for efficient X-ray scintillation and imaging. Nat. Mater. 21, 210–216 (2022).

    Article  ADS  Google Scholar 

  16. Wang, J.-X. et al. Nearly 100% energy transfer at the interface of metal-organic frameworks for X-ray imaging scintillators. Matter 5, 253–265 (2022).

    Article  Google Scholar 

  17. Gandini, M. et al. Efficient, fast and reabsorption-free perovskite nanocrystal-based sensitized plastic scintillators. Nat. Nanotechnol. 15, 462–468 (2020).

    Article  ADS  Google Scholar 

  18. Wang, X. et al. Color-tunable X-ray scintillation based on a series of isotypic lanthanide–organic frameworks. Chem. Commun. 56, 233–236 (2019).

    Article  Google Scholar 

  19. Wang, X. et al. Organic phosphors with bright triplet excitons for efficient X-ray-excited luminescence. Nat. Photon. 15, 187–192 (2021).

    Article  ADS  Google Scholar 

  20. Galunov, N. et al. Delayed radioluminescence of some heterostructured organic scintillators. J. Lumin. 226, 117477 (2020).

    Article  Google Scholar 

  21. Wang, J.-X. et al. Organic thermometers based on aggregation of difluoroboron β-diketonate chromophores. J. Phys. Chem. A 124, 10082–10089 (2020).

    Article  ADS  Google Scholar 

  22. Wang, X. F. et al. Pure organic room temperature phosphorescence from excited dimers in self-assembled nanoparticles under visible and near-infrared irradiation in water. J. Am. Chem. Soc. 141, 5045–5050 (2019).

    Article  Google Scholar 

  23. Zhang, X. et al. Ultralong phosphorescence cellulose with excellent anti-bacterial, water-resistant and ease-to-process performance. Nat. Commun. 13, 1117 (2022).

    Article  ADS  Google Scholar 

  24. Wang, J.-X. et al. Tunable fluorescence and afterglow in organic crystals for temperature sensing. J. Phys. Chem. Lett. 13, 1985–1990 (2022).

    Article  Google Scholar 

  25. Dai, W. et al. Halogen bonding: a new platform for achieving multi-stimuli-responsive persistent phosphorescence. Angew. Chem. Int. Ed. 61, e202200236 (2022).

    Google Scholar 

  26. Jeon, S. O. et al. High-efficiency, long-lifetime deep-blue organic light-emitting diodes. Nat. Photon. 15, 208–215 (2021).

    Article  ADS  Google Scholar 

  27. Hirata, S. et al. Highly efficient blue electroluminescence based on thermally activated delayed fluorescence. Nat. Mater. 14, 330–336 (2015).

    Article  ADS  Google Scholar 

  28. Yang, Z. et al. Recent advances in organic thermally activated delayed fluorescence materials. Chem. Soc. Rev. 46, 915–1016 (2017).

    Article  Google Scholar 

  29. Wang, J.-X. et al. Organic composite crystal with persistent room-temperature luminescence above 650 nm by combining triplet–triplet energy transfer with thermally activated delayed gluorescence. CCS Chem. 2, 1391–1398 (2020).

    Article  Google Scholar 

  30. Ding, D. et al. Highly efficient and color-stable thermally activated delayed fluorescence white light-emitting diodes featured with single-doped single emissive layers. Adv. Mater. 32, e1906950 (2020).

    Article  ADS  Google Scholar 

  31. Luo, D., Chen, Q., Gao, Y., Zhang, M. & Liu, B. Extremely simplified, high-performance, and doping-free white organic light-emitting diodes based on a single thermally activated delayed fluorescent emitter. ACS Energy Lett. 3, 1531–1538 (2018).

    Article  Google Scholar 

  32. Tang, L. et al. X-ray excited ultralong room-temperature phosphorescence for organic afterglow scintillators. Chem. Commun. 56, 13559–13562 (2020).

    Article  Google Scholar 

  33. Dong, C. et al. Influence of isomerism on radioluminescence of purely organic phosphorescence scintillators. Angew. Chem. Int. Ed. 60, 27195–27200 (2021).

    Article  Google Scholar 

  34. Chen, H. et al. Cesium lead halide nanocrystals based flexible X‐ray imaging screen and visible dose rate indication on paper substrate. Adv. Opt. Mater. 10, 2102790 (2022).

    Article  Google Scholar 

  35. Han, L. et al. Photophysics in zero‐dimensional potassium‐doped cesium copper chloride Cs3Cu2Cl5 nanosheets and its application for high‐performance flexible X‐ray detection. Adv. Opt. Mater. 10, 2102453 (2022).

    Article  Google Scholar 

  36. Liu, Y. et al. Large lead‐free perovskite single crystal for high‐performance coplanar X‐ray imaging applications. Adv. Opt. Mater. 8, 2000814 (2020).

    Article  Google Scholar 

  37. Lian, L. et al. Highly luminescent zero-dimensional organic copper halides for X-ray scintillation. J. Phys. Chem. Lett. 12, 6919–6926 (2021).

    Article  Google Scholar 

  38. Zhang, Y. et al. Metal halide perovskite nanosheet for X-ray high-resolution scintillation imaging screens. ACS Nano 13, 2520–2525 (2019).

    Article  Google Scholar 

  39. Wang, J.-X. et al. Perovskite-nanosheet sensitizer for highly efficient organic X-ray imaging scintillator. ACS Energy Lett. 7, 10–16 (2021).

    Article  Google Scholar 

  40. Kretzschmar, A., Patze, C., Schwaebel, S. T. & Bunz, U. H. Development of thermally activated delayed fluorescence materials with shortened emissive lifetimes. J. Org. Chem. 80, 9126–9131 (2015).

    Article  Google Scholar 

  41. Kim, H. S. et al. Enhancement of reverse intersystem srossing in charge‐transfer molecule through internal heavy atom effect. Adv. Funct. Mater. 31, 2104646 (2021).

    Article  Google Scholar 

  42. Berger, M. J. et al. XCOM: Photon Cross Sections Database (National Institute of Standards and Technology, 2013); https://www.nist.gov/pml/xcom-photoncross-sections-database

  43. El-Ballouli, A. O. et al. Quantum confinement-tunable ultrafast charge transfer at the PbS quantum dot and phenyl-C61-butyric acid methyl ester interface. J. Am. Chem. Soc. 136, 6952–6959 (2014).

    Article  Google Scholar 

  44. Wadt, W. R. & Hay, P. J. Ab initio effective core potentials for molecular calculations. Potentials for main group elements Na to Bi. J. Chem. Phys. 82, 284–298 (1985).

    Article  ADS  Google Scholar 

  45. Gao, X. et al. Evaluation of spin-orbit couplings with linear-response time-dependent density functional methods. J. Chem. Theory Comput. 13, 515–524 (2017).

    Article  Google Scholar 

  46. Warburton, W. K., Carlson, J. S. & Feng, P. L. Organic glass scintillator (OGS) property comparisons to stilbene, EJ-276 and BC-404. Nucl. Instrum. Methods Phys. Res. B 1018, 165778 (2021).

    Article  Google Scholar 

  47. Chen, W. et al. All‐inorganic perovskite polymer-ceramics for flexible and refreshable X‐ray imaging. Adv. Funct. Mater. 32, 2107424 (2021).

    Article  Google Scholar 

Download references

Acknowledgements

This work was supported by the King Abdullah University of Science and Technology (KAUST).

Author information

Authors and Affiliations

Authors

Contributions

J.-X.W. and O.F.M. conceived the project. J.-X.W. synthesized the TADF chromophores, prepared the films for measurements and applications, performed the steady-state experiments and some time-resolved experiments, and analysed the data. L.G.A. performed the TA and TCSPC measurements as well as the DFT calculations. J.-X.W., X.W. and Y.Z. performed and analysed the scintillation measurements. T.H. synthesized the CsPbBr3 nanosheet. O.M.B and M.E. contributed to the discussion of the experimental data and provided valuable suggestions. O.F.M. supervised the project and suggested the analysis of the experimental data. J.-X.W. and O.F.M. co-wrote the manuscript.

Corresponding author

Correspondence to Omar F. Mohammed.

Ethics declarations

Competing interests

O.M.B. is a founder of Quantum Solutions, a company that develops optoelectronic devices. The other authors declare no competing interests.

Peer review

Peer review information

Nature Photonics thanks Kris Iniewski and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–8, Tables 1–4 and material synthesis.

Source data

Source Data Fig. 2

Statistical source data.

Source Data Fig. 3

Statistical source data.

Source Data Fig. 4

Statistical source data.

Rights and permissions

Springer Nature or its licensor holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Wang, JX., Gutiérrez-Arzaluz, L., Wang, X. et al. Heavy-atom engineering of thermally activated delayed fluorophores for high-performance X-ray imaging scintillators. Nat. Photon. 16, 869–875 (2022). https://doi.org/10.1038/s41566-022-01092-x

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41566-022-01092-x

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing