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Synthesis-on-substrate of quantum dot solids

Nature volume 612, pages 679–684 (2022)Cite this article

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Abstract

Perovskite light-emitting diodes (PeLEDs) with an external quantum efficiency exceeding 20% have been achieved in both green and red wavelengths1,2,3,4,5; however, the performance of blue-emitting PeLEDs lags behind6,7. Ultrasmall CsPbBr3 quantum dots are promising candidates with which to realize efficient and stable blue PeLEDs, although it has proven challenging to synthesize a monodispersed population of ultrasmall CsPbBr3 quantum dots, and difficult to retain their solution-phase properties when casting into solid films8. Here we report the direct synthesis-on-substrate of films of suitably coupled, monodispersed, ultrasmall perovskite QDs. We develop ligand structures that enable control over the quantum dots’ size, monodispersity and coupling during film-based synthesis. A head group (the side with higher electrostatic potential) on the ligand provides steric hindrance that suppresses the formation of layered perovskites. The tail (the side with lower electrostatic potential) is modified using halide substitution to increase the surface binding affinity, constraining resulting grains to sizes within the quantum confinement regime. The approach achieves high monodispersity (full-width at half-maximum = 23 nm with emission centred at 478 nm) united with strong coupling. We report as a result blue PeLEDs with an external quantum efficiency of 18% at 480 nm and 10% at 465 nm, to our knowledge the highest reported among perovskite blue LEDs by a factor of 1.5 and 2, respectively6,7.

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Fig. 1: Perovskite QD semiconducting solids.
Fig. 2: Formation of SoS of QD films.
Fig. 3: Optical and electrical properties of SoS of QD films.
Fig. 4: PeLED performance and operating stability.

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All data generated or analysed during this study are included in the published article and its Supplementary Information. Other data that support the findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

This work is financially supported by National Key Research and Development Program of China (2022YFE0201500). We acknowledge financial support from the National Natural Science Foundation of China (nos 91956130, 62104116, 22121005 and 52072185). Y.J. acknowledges the project funded by the China Postdoctoral Science Foundation (no. 2021M701773). M.Y. acknowledges financial support from Distinguished Young Scholars of Tianjin (no. 19JCJQJC62000). We thank the staff of beamlines BL17B1, BL14B1, BL19U2, BL19U1 and BL01B1 at SSRF for providing the beam time and User Experiment Assist System of SSRF for their help. This work was partly supported by Analysis Platform of New Matter Structure at Nankai University.

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Author notes

  1. These authors contributed equally: Yuanzhi Jiang, Changjiu Sun, Jian Xu, Saisai Li

Authors and Affiliations

  1. Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Renewable Energy Conversion and Storage Center (RECAST), College of Chemistry, Nankai University, Tianjin, P. R. China

    Yuanzhi Jiang, Changjiu Sun, Saisai Li, Xinliang Fu, Keyu Wei, Tong Zhou, Wei Zhang, Jun Chen & Mingjian Yuan

  2. Haihe Laboratory of Sustainable Chemical Transformations, Tianjin, P. R. China

    Yuanzhi Jiang, Wei Zhang, Jun Chen & Mingjian Yuan

  3. Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, Canada

    Jian Xu, Yuan Liu, Haoyue Wan, Sjoerd Hoogland & Edward H. Sargent

  4. Henan Key Laboratory of Infrared Materials and Spectrum Measures and Applications, College of Physics and Materials Science, Henan Normal University, Xinxiang, P. R. China

    Minghuan Cui, Chaochao Qin & Yufang Liu

  5. College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Nankai University, Tianjin, P. R. China

    Yaqi Liu

  6. Shanghai Synchrotron Radiation Facility (SSRF), Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, P. R. China

    Yingguo Yang

  7. School of Microelectronics, Fudan University, Shanghai, P. R. China

    Yingguo Yang

  8. School of Materials Science and Engineering, Henan Normal University, Xinxiang, P. R. China

    Jien Yang & Shuyan Gao

  9. College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou, P. R. China

    Jun Pan

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Contributions

M.Y. conceived the idea. M.Y., J.C. and E.H.S. guided the project. Y.J. and M.Y. developed the SoS of QD films. C.S., Yuan Liu and H.W. carried out the device fabrication and characterizations. S.L. and Y.Y. carried out GIWAXS measurements and analyses. Y.J., M.C., C.Q. and Yufang Liu performed transient absorption characterizations and analysed the data. J.X., S.H. and E.H.S carried out theoretical calculations. C.S., K.W., T.Z. and W.Z. carried out the TEM characterization. X.F. and Yaqi Liu helped to synthesize the materials and collect the data. J.Y., S.G. and J.P. contributed to the schematics and photographs. Y.J., J.X., J.C., M.Y. and E.H.S. co-wrote the paper. All authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to Edward H. Sargent, Jun Chen or Mingjian Yuan.

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The authors have filed a provisional patent for this work to the China National Intellectual Property Administration (CNIPA).

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Extended data figures and tables

Extended Data Fig. 1 SoS of RGB QD films.

a, PL and absorption spectra of CsPbBr3 and CsPbI3 QD films fabricated via SoS with various ligand concentrations (from 0 to 0.28 M); inset: photographs of QD films under excitation. Since CsPbI3 suffers from phase stability, we were not able to stabilize ultrasmall CsPbI3 QDs with emission wavelength of below 640 nm. b,c, XRD patterns of CsPbBr3 (b) and CsPbI3 (c) QD films. d, Transient absorption spectra of CsPbI3 QD films (641 nm).

Extended Data Fig. 2 TEM characterization for CsPbBr3 QDs.

a–i, TEM images for CsPbBr3 (463 nm) (a–c), CsPbBr3 (478 nm) (d–f) and CsPbBr3 (515 nm) (g–i) QDs. To avoid possible beam damage and phase transition of perovskite QDs, live time was set to ensure a dose rate of below 10 e Å−2 s−1. The inter-planar distance was calculated by average distance value (dadv.) between five lattice fringes. The statistical diameter histogram was obtained by counting over 50 QDs. j, Relationship among ligand concentration, the peak wavelength of QD films and the size of the QDs.

Extended Data Fig. 3 2D formation feasibility of perovskites.

a, Steric effect index (STEI) of PEA+, MBA+ and DMA+ ligands. b, Octahedral distortion index and effective coordination number for PEA+- or MBA+- substituted CsPbBr3 (left) and MBA+- or DMA+-substituted CsPbI3 (right) perovskite slabs. c, Interaction energies (Eint) of adjacent fragments at their interfaces for PEA+- or MBA+-substituted CsPbBr3 perovskite slabs and MBA+- or DMA+-substituted CsPbI3 perovskite slabs. d, Formation energy differences (ΔEf) for CsPbBr3 and CsPbI3 layered perovskites with n values of 1 and 2.

Extended Data Fig. 4 Transient absorption characterization of CsPbBr3 QDs.

a–h, Time-wavelength-dependent transient absorption spectra for CsPbBr3 QD films fabricated via SoS by adding various amounts of ligand (from 0 to 0.28 M).

Extended Data Fig. 5 XRD pattern of the intermediate phase powder.

The intermediate phase powder was obtained via the antisolvent-diffusion method. All the diffraction peaks can be indexed as the PbBr2-2∙DMSO complex.

Extended Data Fig. 6 Steady-state PL characteristics of CsPbBr3 QD films with different capping ligands.

a,b, Steady-state PL spectra (a) and corresponding PL peak positions (b) of CsPbBr3 perovskite QD films with different X-MBA+ ligands.

Extended Data Fig. 7 Morphological properties of perovskite QD films.

a–f, SEM (a–c) and AFM (d–f) images for CsPbBr3 (463 nm; a,d), CsPbBr3 (478 nm; b,e) and CsPbBr3 (515 nm; c,f) QD films. r.m.s., root mean square.

Extended Data Fig. 8 EL performance of RGB PeLEDs.

a, J–L–V curves of the RGB PeLEDs. b, EL spectra of the PeLEDs operating at different voltages. c–e, EL peak position and FWHM evolution as a function of time for the PeLEDs. The operational stability measurement was carried out with initial luminance of ~100 cd m−2. f–i, Half-lifetime (T50) measurements for the PeLEDs.

Extended Data Fig. 9 Histogram of PeLEDs.

a–h, Histograms of peak EQEs (a–d) and maximum luminance (e–h) values for the PeLEDs based on CsPbBr3 (463 nm; a,e), CsPbBr3 (478 nm; b,g), CsPbBr3 (515 nm; c,f), and CsPbI3 (678 nm; d,h) QDs. Detailed data have been provided in Supplementary Note 9.

Extended Data Table 1 Summary of efficient blue PeLEDs (EQE > 5%) reported to date Refs. 6,7,12,13,23,24
Full size table

Supplementary information

Supplementary Information

This file contains Supplementary Notes 1–10, Supplementary Figures 1–22, Supplementary Tables 1–3 and Supplementary References.

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Jiang, Y., Sun, C., Xu, J. et al. Synthesis-on-substrate of quantum dot solids. Nature 612, 679–684 (2022). https://doi.org/10.1038/s41586-022-05486-3

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