Abstract

Organic–inorganic metal halide perovskites have demonstrated high power conversion efficiencies in solar cells and promising performance in a wide range of optoelectronic devices. The existence and stability of bound electron–hole pairs in these materials and their role in the operation of devices with different architectures remains a controversial issue. Here we demonstrate, through a combination of optical spectroscopy and multiscale modelling as a function of the degree of polycrystallinity and temperature, that the electron–hole interaction is sensitive to the microstructure of the material. The long-range order is disrupted by polycrystalline disorder and the variations in electrostatic potential found for smaller crystals suppress exciton formation, while larger crystals of the same composition demonstrate an unambiguous excitonic state. We conclude that fabrication procedures and morphology strongly influence perovskite behaviour, with both free carrier and excitonic regimes possible, with strong implications for optoelectronic devices.

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References

  1. 1.

    et al. Interface engineering of highly efficient perovskite solar cells. Science 345, 542–546 (2014).

  2. 2.

    et al. Compositional engineering of perovskite materials for high-performance solar cells. Nature 517, 476–480 (2015).

  3. 3.

    , , & Low-temperature solution-processed wavelength-tunable perovskites for lasing. Nature Mater. 13, 476–480 (2014).

  4. 4.

    et al. High photoluminescence efficiency and optically pumped lasing in solution-processed mixed halide perovskite semiconductors. J. Phys. Chem. Lett. 5, 1421–1426 (2014).

  5. 5.

    et al. Lead halide perovskite nanowire lasers with low lasing thresholds and high quality factors. Nature Mater. 14, 636–642 (2015).

  6. 6.

    et al. Bright light-emitting diodes based on organometal halide perovskite. Nature Nanotech. 9, 687–692 (2014).

  7. 7.

    , , & Low-temperature processed meso-superstructured to thin-film perovskite solar cells. Energy Environ. Sci. 6, 1739–1743 (2013).

  8. 8.

    , , , & Role of the crystallization substrate on the photoluminescence properties of organo-lead mixed halides perovskites. APL Mater. 2, 081509 (2014).

  9. 9.

    et al. The impact of the crystallization processes on the structural and optical properties of hybrid perovskite films for photovoltaics. J. Phys. Chem. Lett. 5, 3836–3842 (2014).

  10. 10.

    et al. Unravelling the mechanism of photoinduced charge transfer processes in lead iodide perovskite solar cells. Nature Photon. 8, 250–255 (2014).

  11. 11.

    & Band filling with free charge carriers in organometal halide perovskites. Nature Photon. 8, 737–743 (2014).

  12. 12.

    et al. Excitons versus free charges in organo-lead tri-halide perovskites. Nature Commun. 5, 3486 (2014).

  13. 13.

    , , , & Tuning the light emission properties by band gap engineering in hybrid lead-halide perovskite. J. Am. Chem. Soc. 136, 17730–17733 (2014).

  14. 14.

    , , , & Electro-optics of perovskite solar cells. Nature Photon. 9, 106–112 (2014).

  15. 15.

    et al. Correlated electron–hole plasma in organometal perovskites. Nature Commun. 5, 5049 (2014).

  16. 16.

    et al. Direct measurement of the exciton binding energy and effective masses for charge carriers in an organic–inorganic tri-halide perovskite. Nature Phys. 11, 582–587 (2015).

  17. 17.

    et al. Low trap-state density and long carrier diffusion in organolead trihalide perovskite single crystals. Science 347, 519–522 (2015).

  18. 18.

    et al. Electron–hole diffusion lengths >175 μm in solution-grown CH3NH3PbI3 single crystals. Science 347, 967–970 (2015).

  19. 19.

    et al. High-efficiency solution-processed perovskite solar cells with millimeter-scale grains. Science 347, 522–525 (2015).

  20. 20.

    , , , & Growth of CH3NH3PbI3 cuboids with controlled size for high-efficiency perovskite solar cells. Nature Nanotech. 9, 927–932 (2014).

  21. 21.

    et al. Long-range balanced electron- and hole-transport lengths in organic–inorganic CH3NH3PbI3. Science 342, 344–347 (2013).

  22. 22.

    Temperature dependence of the energy gap in semiconductors. Physica 34, 149–154 (1967).

  23. 23.

    , & Calorimetric and IR spectroscopic studies of phase transitions in methylammonium trihalogenoplumbates (II). J. Phys. Chem. Solids 51, 1383–1395 (1990).

  24. 24.

    , & Influence of dielectric confinement on excitonic nonlinearity in inorganic–organic layered semiconductors. Phys. Rev. B 71, 205306 (2005).

  25. 25.

    et al. Well-size dependence of exciton blue shift in GaAs multiple-quantum-well structures. Phys. Rev. B 33, 4389–4391 (1986).

  26. 26.

    et al. Blue shift of the exciton resonance due to exciton–exciton interactions in a multiple-quantum-well structure. Phys. Rev. Lett. 53, 2433–2436 (1984).

  27. 27.

    , & Theory of transient excitonic optical nonlinearities in semiconductor quantum-well structures. Phys. Rev. B 32, 6601–6609 (1985).

  28. 28.

    , & Excitonic many-body interactions in two-dimensional lead iodide perovskite quantum wells. J. Phys. Chem. C 119, 14714–14721 (2015).

  29. 29.

    , & The raman spectrum of the CH3NH3PbI3 hybrid perovskite: interplay of theory and experiment. J. Phys. Chem. Lett. 5, 279–284 (2014).

  30. 30.

    et al. Solid-state physics perspective on hybrid perovskite semiconductors. J. Phys. Chem. C 119, 10161–10177 (2015).

  31. 31.

    , & Planar CH3NH3PbBr3 hybrid solar cells with 10.4% power conversion efficiency, fabricated by controlled crystallization in the spin-coating process. Adv. Mater. 26, 8179–8183 (2014).

  32. 32.

    , , & High open-circuit voltage solar cells based on organic–inorganic lead bromide perovskite. J. Phys. Chem. Lett. 4, 897–902 (2013).

  33. 33.

    et al. Comparative study on the excitons in lead-halide-based perovskite-type crystals CH3NH3PbBr3CH3NH3PbI3. Solid State Commun. 127, 619–623 (2003).

  34. 34.

    et al. Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics. Chem. Sci. 6, 613–617 (2014).

  35. 35.

    & Preparation of single-phase films of CH3NH3Pb(I1–xBrx)3 with sharp optical band edges. J. Phys. Chem. Lett. 5, 2501–2505 (2014).

  36. 36.

    , , , & Structural and electronic properties of organo-halide lead perovskites: a combined IR-spectroscopy and ab initio molecular dynamics investigation. Phys. Chem. Chem. Phys. 16, 16137–16144 (2014).

  37. 37.

    , & Cation rotation in methylammonium lead halides. Solid State Commun. 56, 581–582 (1985).

  38. 38.

    & Dynamic disorder in methylammoniumtrihalogenoplumbates (II) observed by millimeter-wave spectroscopy. J. Chem. Phys. 87, 6373 (1987).

  39. 39.

    , & Molecular ferroelectric contributions to anomalous hysteresis in hybrid perovskite solar cells. APL Mater. 2, 081506 (2014).

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Acknowledgements

The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 604032 of the MESO project, under grant agreement 316494 (DESTINY), the EU Horizon 2020 Research and Innovation Programme under grant agreement no. 643238 (SYNCHRONICS) and from Fondazione Cariplo (project GREENS no. 2013-0656). J.M.F. is funded by the EPSRC (EP/K016288/ and EP/M009580/1), and A.W. is supported by the European Research Council (project no. 277757). The authors thank S. Neutzner for help with fs-TA experiments and W. Xu for help with sample preparation. The authors thank E.T. Hoke, E.R. Dohner and H. Karunadasa for discussions and for providing the single crystal. The authors thank L. Manna for discussions and access to the XRD facility.

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Author notes

    • Giulia Grancini
    •  & Ajay Ram Srimath Kandada

    These authors contributed equally to this work

Affiliations

  1. Center for Nano Science and Technology @Polimi, Istituto Italiano di Tecnologia, via Giovanni Pascoli 70/3, Milan 20133, Italy

    • Giulia Grancini
    • , Ajay Ram Srimath Kandada
    • , Alex J. Barker
    • , Michele De Bastiani
    • , Marina Gandini
    • , Guglielmo Lanzani
    •  & Annamaria Petrozza
  2. Centre for Sustainable Chemical Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK

    • Jarvist M. Frost
    •  & Aron Walsh
  3. Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, Padova 35131, Italy

    • Michele De Bastiani
  4. Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci, 32, 20133 Milano, Italy

    • Marina Gandini
    •  & Guglielmo Lanzani
  5. Department of Nanochemistry, Istituto Italiano di Tecnologia, via Morego 30, Genova 16163, Italy

    • Sergio Marras

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Contributions

G.G., A.R.S.K. and A.J.B. performed the transient absorption measurements. M.G. and M.D.B. prepared the samples and characterized them by SEM. S.M. performed XRD and SEM characterization. G.G., A.R.S.K., G.L. and A.P. analysed the optical spectroscopy data. J.M.F. and A.W. performed the multiscale modelling and analysed the results. The manuscript was written with contributions from all authors. A.P. supervised the project.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Annamaria Petrozza.

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DOI

https://doi.org/10.1038/nphoton.2015.151

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