A fabrication process for flexible single-crystal perovskite devices

Abstract

Organic–inorganic hybrid perovskites have electronic and optoelectronic properties that make them appealing in many device applications1,2,3,4. Although many approaches focus on polycrystalline materials5,6,7, single-crystal hybrid perovskites show improved carrier transport and enhanced stability over their polycrystalline counterparts, due to their orientation-dependent transport behaviour8,9,10 and lower defect concentrations11,12. However, the fabrication of single-crystal hybrid perovskites, and controlling their morphology and composition, are challenging12. Here we report a solution-based lithography-assisted epitaxial-growth-and-transfer method for fabricating single-crystal hybrid perovskites on arbitrary substrates, with precise control of their thickness (from about 600 nanometres to about 100 micrometres), area (continuous thin films up to about 5.5 centimetres by 5.5 centimetres), and composition gradient in the thickness direction (for example, from methylammonium lead iodide, MAPbI3, to MAPb0.5Sn0.5I3). The transferred single-crystal hybrid perovskites are of comparable quality to those directly grown on epitaxial substrates, and are mechanically flexible depending on the thickness. Lead–tin gradient alloying allows the formation of a graded electronic bandgap, which increases the carrier mobility and impedes carrier recombination. Devices based on these single-crystal hybrid perovskites show not only high stability against various degradation factors but also good performance (for example, solar cells based on lead–tin-gradient structures with an average efficiency of 18.77 per cent).

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Fig. 1: The lithography-assisted epitaxial-growth-and-transfer method for fabricating high-quality, single-crystal hybrid perovskite thin films.
Fig. 2: Thickness-dependent carrier transport and mechanical properties of the single-crystal hybrid perovskite.
Fig. 3: Bandgap-graded single-crystal perovskite thin films.
Fig. 4: Flexible bandgap-graded single-crystal perovskite photovoltaics.

Data availability

The data that support the findings of this study are available from the corresponding authors on reasonable request.

References

  1. 1.

    Yang, W. S. et al. Iodide management in formamidinium-lead-halide-based perovskite layers for efficient solar cells. Science 356, 1376–1379 (2017).

    ADS  CAS  Article  Google Scholar 

  2. 2.

    Lin, K. et al. Perovskite light-emitting diodes with external quantum efficiency exceeding 20 per cent. Nature 562, 245–248 (2018).

    ADS  CAS  Article  Google Scholar 

  3. 3.

    Feng, J. et al. Single-crystalline layered metal-halide perovskite nanowires for ultrasensitive photodetectors. Nat. Electron. 1, 404–410 (2018).

    CAS  Article  Google Scholar 

  4. 4.

    National Renewable Energy Laboratory. Best Research-Cell Efficiency Chart https://www.nrel.gov/pv/cell-efficiency.html (NREL, US Department of Energy, 2020).

  5. 5.

    Wang, Q. et al. Large fill-factor bilayer iodine perovskite solar cells fabricated by a low-temperature solution-process. Energy Environ. Sci. 7, 2359–2365 (2014).

    CAS  Article  Google Scholar 

  6. 6.

    Liu, Z. et al. Gas–solid reaction based over one-micrometer-thick stable perovskite films for efficient solar cells and modules. Nat. Commun. 9, 3880 (2018).

    ADS  Article  Google Scholar 

  7. 7.

    Jiang, Q. et al. Surface passivation of perovskite film for efficient solar cells. Nat. Photon. 13, 460–466 (2019); correction 13, 500 (2019).

    CAS  Google Scholar 

  8. 8.

    Leblebici, S. Y. et al. Facet-dependent photovoltaic efficiency variations in single grains of hybrid halide perovskite. Nat. Energy 1, 16093 (2016).

    ADS  CAS  Article  Google Scholar 

  9. 9.

    Zhang, W. et al. Enhanced optoelectronic quality of perovskite thin films with hypophosphorous acid for planar heterojunction solar cells. Nat. Commun. 6, 10030 (2015).

    ADS  CAS  Article  Google Scholar 

  10. 10.

    Zheng, G. et al. Manipulation of facet orientation in hybrid perovskite polycrystalline films by cation cascade. Nat. Commun. 9, 2793 (2018).

    ADS  Article  Google Scholar 

  11. 11.

    Chen, Z. et al. Thin single-crystal perovskite solar cells to harvest below-bandgap light absorption. Nat. Commun. 8, 1890 (2017).

    ADS  Article  Google Scholar 

  12. 12.

    Lee, L. et al. Wafer-scale single-crystal perovskite patterned thin films based on geometrically-confined lateral crystal growth. Nat. Commun. 8, 15882 (2017).

    ADS  CAS  Article  Google Scholar 

  13. 13.

    Lei, Y. et al. Controlled homoepitaxial growth of hybrid perovskites. Adv. Mater. 30, 1705992 (2018).

    ADS  Article  Google Scholar 

  14. 14.

    Chen, Y. et al. Strain engineering and epitaxial stabilization of halide perovskites. Nature 577, 209–215 (2020).

    ADS  CAS  Article  Google Scholar 

  15. 15.

    Zou, W. et al. Minimising efficiency roll-off in high-brightness perovskite light-emitting diodes. Nat. Commun. 9, 608 (2018).

    ADS  Article  Google Scholar 

  16. 16.

    Richter, J. M. et al. Enhancing photoluminescence yields in lead halide perovskites by photon recycling and light out-coupling. Nat. Commun. 7, 13941 (2016).

    ADS  CAS  Article  Google Scholar 

  17. 17.

    Gong, X. et al. Contactless measurements of photocarrier transport properties in perovskite single crystals. Nat. Commun. 10, 1591 (2019).

    ADS  Article  Google Scholar 

  18. 18.

    Tsai, H. et al. Design principles for electronic charge transport in solution-processed vertically stacked 2D perovskite quantum wells. Nat. Commun. 9, 2130 (2018).

    ADS  Article  Google Scholar 

  19. 19.

    Ćirić, L. et al. Mechanical response of CH3NH3PbI3 nanowires. Appl. Phys. Lett. 112, 111901 (2018).

    ADS  Article  Google Scholar 

  20. 20.

    Bokdam, M. et al. Role of polar phonons in the photo excited state of metal halide perovskites. Sci. Rep. 6, 28618 (2016).

    ADS  CAS  Article  Google Scholar 

  21. 21.

    Noel, N. K. et al. Lead-free organic-inorganic tin halide perovskites for photovoltaic applications. Energy Environ. Sci. 7, 3061–3068 (2014).

    CAS  Article  Google Scholar 

  22. 22.

    Tong, J. et al. Carrier lifetimes of >1 μs in Sn-Pb perovskites enable efficient all-perovskite tandem solar cells. Science 364, 475–479 (2019).

    ADS  CAS  Article  Google Scholar 

  23. 23.

    Dullweber, T., Rau, U. & Schock, H. A new approach to high-efficiency solar cells by band gap grading in Cu(In, Ga)Se2 chalcopyrite semiconductors. Sol. Energy Mater. Sol. Cells 67, 145–150 (2001).

    CAS  Article  Google Scholar 

  24. 24.

    Hutchby, J. A. & Fudurich, R. L. Theoretical analysis of AlxGa1−xAs-GaAs graded band-gap solar cell. J. Appl. Phys. 47, 3140–3151 (1976).

    ADS  CAS  Article  Google Scholar 

  25. 25.

    Wang, C., Wang, C., Huang, Z. & Xu, S. Materials and structures toward soft electronics. Adv. Mater. 30, 1801368 (2018).

    Article  Google Scholar 

  26. 26.

    Wang, S., Jiang, Y., Juarez-Perez, E. J., Ono, L. K. & Qi, Y. Accelerated degradation of methylammonium lead iodide perovskites induced by exposure to iodine vapour. Nat. Energy 2, 16195 (2017).

    ADS  CAS  Article  Google Scholar 

  27. 27.

    Yun, J. S. et al. Humidity-induced degradation via grain boundaries of HC(NH2)2PbI3 planar perovskite solar cells. Adv. Funct. Mater. 28, 1705363 (2018).

    Article  Google Scholar 

  28. 28.

    Tsai, H. et al. Light-induced lattice expansion leads to high-efficiency perovskite solar cells. Science 360, 67–70 (2018).

    ADS  CAS  Article  Google Scholar 

  29. 29.

    Ke, W. & Kanatzidis, M. G. Prospects for low-toxicity lead-free perovskite solar cells. Nat. Commun. 10, 965 (2019).

    ADS  Article  Google Scholar 

  30. 30.

    Chen, M. et al. Highly stable and efficient all-inorganic lead-free perovskite solar cells with native-oxide passivation. Nat. Commun. 10, 16 (2019).

    ADS  CAS  Article  Google Scholar 

  31. 31.

    Domanski, K., Alharbi, E. A., Hagfeldt, A., Grätzel, M. & Tress, W. Systematic investigation of the impact of operation conditions on the degradation behaviour of perovskite solar cells. Nat. Energy 3, 61–67 (2018).

    ADS  CAS  Article  Google Scholar 

  32. 32.

    Ono, L. K., Qi, Y. & Liu, S. F. Progress toward stable lead halide perovskite solar cells. Joule 2, 1961–1990 (2018).

    CAS  Article  Google Scholar 

  33. 33.

    Liu, M., Jing, D., Zhou, Z. & Guo, L. Twin-induced one-dimensional homojunctions yield high quantum efficiency for solar hydrogen generation. Nat. Commun. 4, 2278 (2013).

    ADS  Article  Google Scholar 

  34. 34.

    Ahn, N. et al. Highly reproducible perovskite solar cells with average efficiency of 18.3% and best efficiency of 19.7% fabricated via Lewis base adduct of lead (II) iodide. J. Am. Chem. Soc. 137, 8696–8699 (2015).

    CAS  Article  Google Scholar 

  35. 35.

    Zhao, P. et al. Antisolvent with an ultrawide processing window for the one-step fabrication of efficient and large-area perovskite solar cells. Adv. Mater. 30, 1802763 (2018).

    Article  Google Scholar 

Download references

Acknowledgements

We thank S. Shrestha for discussions on the polycrystalline device fabrication, S. Wang for analysis and discussions on the UPS, Y. Wang for discussions on the adhesion force measurement, J. Wu for analysis and discussion of the EBIC and S. Xiang for feedback on the manuscript preparation. This work was supported by the start-up fund by University of California San Diego. D.P.F. acknowledges California Energy Commission award no. EPC-16-050. The microfabrication involved in this work was in part performed at the San Diego Nanotechnology Infrastructure (SDNI) of UCSD, a member of the National Nanotechnology Coordinated Infrastructure, which was supported by the National Science Foundation (grant number ECCS-1542148). This characterization work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the US Department of Energy (DOE) Office of Science by Los Alamos National Laboratory (contract 89233218CNA000001) and Sandia National Laboratories (contract DE-NA-0003525).

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Authors

Contributions

S.X. and Y. Lei conceived the idea. Y. Lei and Y.C. contributed to the growth and transfer method. Y. Lei and Y.C. took the optical and SEM images. Y. Lei and R.Z. carried out the photovoltaic-related characterizations. Y. Lei carried out the EBIC measurements. R.Z. carried out the XRD characterizations. Yuheng Li and K.Y. carried out the DFT calculations. Q.Y. and J.L. contributed to the TEM and XPS characterizations. S.L. carried out the finite element analysis. Y. Lei, Y.Y., H.T., W.C., K.W., Y. Luo, D.P.F., S.A.D., J.Y., W.N. and Y.-H.L. contributed to the carrier dynamic measurement and analysis. Y. Lei, Y.C., Y.G. and Chunfeng Wang contributed to the device fabrication. Y. Lei, S.L., M.L. and M.P. contributed to the flexibility characterizations. X.Z. carried out the FDTD calculations. Y. Lei, Chonghe Wang, H.H., Yang Li, B.Q. and Z.Z. contributed to the schematics and photographs. All authors contributed to discussing the data and commenting on the manuscript.

Corresponding author

Correspondence to Sheng Xu.

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The authors declare no competing interests.

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Peer review information Nature thanks Hyunhyub Ko and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Fig. 1 The mechanism of the lithography-assisted epitaxial-growth-and-transfer method.

a, Detailed schematic growth steps. Lp, pattern width; Ld, distance between two patterns; Lx–y, growth length in the x–y plane; Lz, growth length in the vertical z direction. b, Detailed epitaxial merging steps shown by SEM images (top view). First, individual single-crystals grow out of the mask. The lattice orientation of the epitaxial crystals is the same, which is controlled by the substrate. Then the individual crystals gradually expand and contact with each other. No lattice tilting or twisting can be found. Finally, completely merged single-crystal thin films are formed, where no grain boundaries can be seen. c, Titled SEM images of different growth behaviour under different growth temperatures and precursor concentrations. Low temperature and concentration can result in thin films (left), whereas high temperature and concentration lead to rods (right).

Extended Data Fig. 2 Characterizations of interfacial crystal quality.

High-resolution TEM studies of transferred single-crystal MAPbI3 on different substrates (for example, gold for metals, glass for oxides and PDMS for polymers) using this growth-and-transfer method. The results show that there is no obvious lattice dislocation or polycrystalline structure formed at the interface, indicating that the re-adhesion/re-growth process maintains the single-crystal properties of the transferred materials.

Extended Data Fig. 3 Scaling up the fabrication method.

a, Freestanding transferred single-crystal MAPbI3 thin films fabricated by soft polymer masks and corresponding bulk substrates. b, A large bulk substrate (left) that is used to epitaxially grow the single-crystal MAPbI3 thin film (left) and a transferred single-crystal MAPbI3 thin film using a rigid copper foil (20 μm thick) as the mask (right).

Extended Data Fig. 4 Carrier diffusion length calculations.

ac, Carrier diffusion lengths (a) calculated from measured carrier mobilities (b) and carrier lifetimes (c) with different thicknesses of the single-crystal perovskite. Insufficient charge collection begins when the thickness goes beyond about 5 μm, which can result in a high recombination possibility in the absorber and thus a low device efficiency. Error bars come from three different measurements under the same condition.

Extended Data Fig. 5 The NMP design.

a, Schematics for calculating the position of the NMP. The SU-8/PDMS top layer is critical for minimizing the strain in the single-crystal perovskite layer. b, Optical (left) and SEM (right) images under different bending conditions. The single-crystal perovskite (about 2 μm thick) can be successfully bent to r ≈ 2.5 mm. All optical images share the same scale bar. All SEM images share the same scale bar.

Extended Data Fig. 6 The growth setup for the bandgap-graded single-crystal perovskites.

a, Schematic growth processes with continuously exchanging the precursor solution, which allows the formation of the alloyed structure along the epitaxial growth direction. The perovskite substrate sits in a PDMS growth mould in precursor solution 1. A different precursor solution 2 is fed with designed rates (depending on the solution volume, a calculation example can be seen in Supplementary Discussion 1). b, Optical images showing two representative kinds of graded single-crystal perovskites. The alloyed region is at the interface (about 1 mm in width, depending on the alloying rate) between the different coloured crystals. Organic cations, inorganic atoms and halides can all be alloyed.

Extended Data Fig. 7 Density-functional theory simulations of the graded single-crystal perovskites.

a, Calculation results showing electronic band structures of the graded single-crystal MAPb0.5+xSn0.5−xI3. All structures show direct bandgaps at the Γ point. The Fermi level is normalized to the VBM, to show the shrinking tendency of the bandgap. b, Calculated effective masses for electrons and holes in the graded single-crystal MAPb0.5+xSn0.5−xI3 with an increasing tin concentration. The decreasing effective masses indicate increasing mobilities of both electrons and holes. The enhancement for holes is more pronounced than for electrons. c, Graded single-crystal MAPb0.5+xSn0.5−xI3 (left) showing a graded bandgap in comparison with the flat bandgap of conventional MAPbI3 (right).

Extended Data Fig. 8 Single-crystal perovskite thin-film light-emitting diodes and photodetectors fabricated using this growth-and-transfer method.

a, Transferred single-crystal MAPbBr3 arrays with each pixel about 100 μm by 100 μm. Inset: the transferred single-crystal MAPbI3 micro light-emitting diode arrays with each pixel about 1 μm by 1 μm. b, SEM images showing the textured single-crystal MAPbI3 thin film as a photodetector. Inset: a magnified SEM image of the cross-sectional structure of the device. PI, polyimide. c, Finite-difference time-domain optical simulation of the overall absorption by the textured structure (left) and the flat structure (right). The absorption by the textured thin film is much higher than that by the flat one because of the anti-reflective effect. d, EQE measurements of different device morphologies. The textured single-crystal film shows the highest quantum efficiency, which comes from the reduced surface reflections. e, Dark current measurements on both textured and flat single-crystal devices show that the current levels are similar, indicating the pinhole-free and high-quality thin films. The higher light current of the textured device reveals its higher absorption compared with the flat device. f, Responsivity results show that the textured devices are more sensitive to the input power. The inset shows that the textured devices exhibit a higher detectivity than the flat devices. The decreasing tendencies of the responsivity and detectivity at high input power may be due to the material degradation under strong light intensities.

Extended Data Fig. 9 In situ XPS depth profile studies of different crystal structures.

In the single-crystal sample, only the surface areas are easy to be oxidized, indicating that the self-doping in deep areas away from the surface is relatively slow. In the polycrystalline sample, the oxidation is much faster in deep areas compared with the single-crystal samples, indicating that the grain boundaries facilitate the oxidation process.

Extended Data Fig. 10 Long-time continuous illumination stability tests.

ad, Summarized tracking results of JSC (a), VOC (b), FF (c) and PCE (d). The differences between single-crystal and polycrystalline devices are not as large as for the shelf-stability tests in Fig. 4f, which may be because of the poor thermal stability of the hole transport layer (spiro) used in all of these devices. In any case, relatively speaking, single-crystal devices show a better stability than polycrystalline devices.

Supplementary information

Supplementary Information

This file contains Supplementary Discussions 1 to 14, Supplementary Figures 1 to 41, Supplementary Table 1, and Supplementary References.

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Lei, Y., Chen, Y., Zhang, R. et al. A fabrication process for flexible single-crystal perovskite devices. Nature 583, 790–795 (2020). https://doi.org/10.1038/s41586-020-2526-z

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