Abstract
Tin (Sn)-based perovskites are promising for realizing lead-free perovskite light-emitting diodes1,2, yet achieving high efficiency devices remains a significant challenge due to the presence of high density of defects in Sn perovskites3,4. The formation of defects in Sn perovskites is still not well understood. Here, by using in-situ spectroscopy, we reveal that major defects in Sn perovskites instantly form during the fast aggregation of clusters at the initial growth process (~15 s from the start of the spin-coating process) and ~80% of the luminescence intensity is quenched within 6 s. We further find that additives that form strong chemical interactions with tin (II) iodide in precursor solutions can effectively prevent the fast aggregation of clusters and avoid the formation of luminescence quenchers. With this approach, efficient near-infrared lead-free perovskite light-emitting diodes with an external quantum efficiency of 8.3% are demonstrated.
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Data availability
The data that support the finding of this study are available from the corresponding authors upon reasonable request.
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Acknowledgements
This work is financially supported by the National Key Research and Development Program of China (2022YFA1204800), the National Natural Science Foundation of China (62288102, 61961160733, 61935017, 62134007, 52233011).
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Jianpu Wang had the idea for and designed the experiments. N.W., J.C., Jianpu Wang and W.H. supervised the work. H.M. carried out device fabrication and characterizations with the assistance of N.C. and J.C. The optical experiments were conducted by Y.T., F.Z., X.B., S.X., S.W. and H.S. The XRD measurement was performed by Y.T. The NMR measurements were conducted by Z.F. and N.Z., and L.Z. supervised this characterization. Jiaqi Wang and D.Q. performed the AFM measurements. L.Y. and Z.K. carried out SEM measurements. N.W. wrote the first draft of the paper and Jianpu Wang provided major revisions.
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Extended data
Extended Data Fig. 1 Illustration of in-situ PL measurements during the formation of perovskite films.
a, Spin-coating process. b, Annealing process.
Extended Data Fig. 2 Characterization of VmB1-based FA0.9Cs0.1SnI3 perovskites.
a, Contour plot of the PL spectra of perovskite during the spin-coating process. b, PL peak and PL intensity of perovskite during the spin-coating process. c, Excitation-intensity-dependent PLQE. d, XRD data. It shows that the inclusion of VmB1 has no notable effect on the crystallization of FA0.9Cs0.1SnI3. e, SEM image (scale bar, 1 μm). The film shows increased film coverage.
Extended Data Fig. 3 Characterization of Sn-based perovskite films with various annealing times.
a–c, PL spectra of FA0.9Cs0.1SnI3 perovskites without (a) or with PEAI (b), PEAI and VmB1 (c), as additives. The samples were prepared by annealing for different times. d–f, Contour plot of in-situ PL spectra of FA0.9Cs0.1SnI3 perovskites without (d) or with PEAI (e), PEAI and VmB1 (f), as additives. The measurements were carried out during the thermal annealing process. g–i, XRD data of FA0.9Cs0.1SnI3 perovskites without (g) or with PEAI (h), PEAI and VmB1 (i), as additives.
Extended Data Fig. 4 Time-resolved PL decay transients of perovskite films with various additives.
a, Without additive. b, With PEAI. c, With PEAI and VmB1. The trap densities are (2 ± 1) × 1017, (7 ± 2) × 1016 and (9 ± 1) × 1015 cm−3 for samples without, with PEAI or PEAI+VmB1 additives through fits from the generic kinetic model19.
Extended Data Fig. 5 In-situ PL measurements of Sn-based perovskites with various additives during the spin-coating process.
a, Tetrabutylammonium chloride. b, Tetraphenylphosphonium chloride. c, Trioctylamine. d, Triphenyl phosphine. e, 4-Aminopyrimidine. f, 2-Naphthylamine. g, Pyrimidine. h, Pyridine. i, Thiophene. j, Pentanol. It shows that the Tetrabutylammonium chloride or Tetraphenylphosphonium chloride can effectively suppress the PL quenching effect compared with Trioctylamine or Triphenyl phosphine, suggesting the cation of additives plays an important role in eliminating the PL quenching of tin perovskite. Moreover, the 4-Aminopyrimidine (the fragment of VmB1) and 2-Naphthylamine also can reduce the PL quenching of tin perovskite, which indicates that additives with –NH2 group also can impede the fast aggregation of clusters.
Extended Data Fig. 6 1H NMR spectra (DMSO-d6, 500 MHz) of perovskite precursor solutions.
a, PEAI-VmB1 based perovskite solution. b, PEAI based perovskite solution. The chemical structures of VmB1, PEAI and FAI are inserted.
Extended Data Fig. 7 Schematic illustration of the growth pathways of FA0.9Cs0.1SnI3 perovskites with PEAI or VmB1 alone.
a, With PEAI. The interaction between PEAI and FAI can facilitate oriented growth. b, With VmB1. VmB1 molecules can effectively suppress the aggregation of Sn-based perovskite clusters.
Extended Data Fig. 8 XPS spectra.
a-d, XPS spectra of VmB1, VmB1 and SnI2, 3D perovskite and VmB1-based perovskite, N 1s spectra (a), S 1s spectra (b), Sn 3d spectra (c), I 3d spectra (d). The perovskite with VmB1 has additional N 1s and S 1s signals from VmB1 compared with the control perovskite film, suggesting the existence of VmB1 on the shallow sub-surfaces. Because of the large molecular size, the VmB1 should be expelled to crystal surfaces during crystallization, which can passivate defects of perovskites. When VmB1 is mixed with SnI2 or introduced into the control perovskite, the N 1s (C-N) and S 1s signals of VmB1 are shifted to higher energies, while the Sn 3d and I 3d signals are shifted to lower energies. This indicates that the –NH2 group of VmB1 can bind to tin iodide octahedra through hydrogen bond interaction or Lewis acid-base interaction, and the S atom of VmB1 also can bind to tin iodide octahedron through Lewis acid-base interaction. e, Sn 3d spectra of the control, PEAI, VmB1 and PEAI+VmB1 based perovskite films. The black and olive lines are the raw data and background data respectively. The ratio of Sn4+/(Sn2++Sn4+) in the control, PEAI, VmB1 and PEAI+VmB1 samples are 21%, 11%, 6% and 6%, respectively.
Extended Data Fig. 9 Perovskite films and LEDs with various VmB1 amounts.
a, Contour plot of PL spectra of perovskites with various VmB1 amounts during the spin-coating process. The 0.15-ratio VmB1 is the sample with 0.04 M VmB1. b, XRD data. c, Excitation-intensity-dependent PLQE. d, PL spectra. e, SEM images (scale bar, 1 μm). f, Current density and radiance versus voltage. g, Dependence of EQE on current density. h, EL spectra.
Extended Data Fig. 10 Characterization of Sn-based perovskites with various additives.
a-c, Contour plot of in situ PL spectra of FA0.9Cs0.1SnI3 perovskites with TMAC (a), TEAC (b) and TBAC (c) as additives during the spin-coating process. Inset, the chemical structures of the additives. d-f, AFM images of FA0.9Cs0.1SnI3 perovskites with TMAC (d), TEAC (e) and TBAC (f) as additives. Scale bar, 1 μm. g, Excitation-intensity-dependent PLQE.
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Supplementary Figs. 1–5, Table 1 and References.
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Min, H., Chang, J., Tong, Y. et al. Additive treatment yields high-performance lead-free perovskite light-emitting diodes. Nat. Photon. 17, 755–760 (2023). https://doi.org/10.1038/s41566-023-01231-y
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DOI: https://doi.org/10.1038/s41566-023-01231-y
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