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Spatially segregated free-carrier and exciton populations in individual lead halide perovskite grains

Nature Photonics volume 11, pages 285–288 (2017)Cite this article

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Abstract

The nature of charge carriers in methylammonium lead iodide perovskites (MAPbI3) at room temperature is still a matter of considerable debate1,2,3. Here, we demonstrate that within single grains of MAPbI3, strong spatial heterogeneities on the nanometre length scale are present and associated with simultaneous free-carrier and exciton populations. These heterogeneous populations, hidden in ensemble measurements, have a signature of spatially resolved relaxation dynamics for above-bandgap photoexcitation. Using spectrally resolved transient absorption microscopy, we directly observe both red- and blueshifts of the band-edge absorption across individual grains due to a dynamic Stark shift and screening of excitonic transitions by hot carriers. These observations help address a long-standing debate on the identity of the charge carriers, showing that both excitons and free carriers coexist, but are spatially segregated on the length scale of hundreds of nanometres.

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Figure 1: Spectrally integrated transient absorption microscopy (TAM) of perovskite grains.
Figure 2: Spectrally resolved pump–probe dynamics of perovskite grain heterogeneities.
Figure 3: Spatially dependent redshift and blueshift of the band edge.
Figure 4: Redshift and blueshift power dependence.

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References

  1. Trinh, M. T., Wu, X. X., Niesner, D. & Zhu, X. Y. Many-body interactions in photo-excited lead iodide perovskite. J. Mater. Chem. A 3, 9285–9290 (2015).

    Article  Google Scholar 

  2. Sheng, C. X. et al. Exciton versus free carrier photogeneration in organometal trihalide perovskites probed by broadband ultrafast polarization memory dynamics. Phys. Rev. Lett. 114, 116601 (2015).

    Article  ADS  Google Scholar 

  3. Simpson, M. J., Doughty, B., Yang, B., Xiao, K. & Ma, Y.-Z. Spatial localization of excitons and charge carriers in hybrid perovskite thin films. J. Phys. Chem. Lett. 6, 3041–3047 (2015).

    Article  Google Scholar 

  4. Gao, P., Gratzel, M. & Nazeeruddin, M. K. Organohalide lead perovskites for photovoltaic applications. Energy Environ. Sci. 7, 2448–2463 (2014).

    Article  Google Scholar 

  5. Yang, B. et al. Perovskite solar cells with near 100% internal quantum efficiency based on large single crystalline grains and vertical bulk heterojunctions. J. Am. Chem. Soc. 137, 9210–9213 (2015).

    Article  Google Scholar 

  6. Son, D.-Y. et al. Self-formed grain boundary healing layer for highly efficient CH3NH3PbI3 perovskite solar cells. Nat. Energy 1, 16081 (2016).

    Article  ADS  Google Scholar 

  7. Park, N. G. Perovskite solar cells: an emerging photovoltaic technology. Mater. Today 18, 65–72 (2015).

    Article  Google Scholar 

  8. Tan, Z. K. et al. Bright light-emitting diodes based on organometal halide perovskite. Nat. Nanotech. 9, 687–692 (2014).

    Article  ADS  Google Scholar 

  9. D'Innocenzo, V. et al. Excitons versus free charges in organo-lead tri-halide perovskites. Nat. Commun. 5, 3586 (2014).

    Article  ADS  Google Scholar 

  10. Miyata, A. et al. Direct measurement of the exciton binding energy and effective masses for charge carriers in organic–inorganic tri-halide perovskites. Nat. Phys. 11, 582–588 (2015).

    Article  Google Scholar 

  11. Motta, C., El-Mellouhi, F. & Sanvito, S. Charge carrier mobility in hybrid halide perovskites. Sci. Rep. 5, 12746 (2015).

    Article  ADS  Google Scholar 

  12. Johnston, M. B. & Herz, L. M. Hybrid perovskites for photovoltaics: charge-carrier recombination, diffusion, and radiative efficiencies. Acc. Chem. Res. 49, 146–154 (2016).

    Article  Google Scholar 

  13. Guo, Z., Manser, J. S., Wan, Y., Kamat, P. V. & Huang, L. B. Spatial and temporal imaging of long-range charge transport in perovskite thin films by ultrafast microscopy. Nat. Commun. 6, 7471 (2015).

    Article  ADS  Google Scholar 

  14. Sun, S. Y. et al. The origin of high efficiency in low-temperature solution-processable bilayer organometal halide hybrid solar cells. Energy Environ. Sci. 7, 399–407 (2014).

    Article  Google Scholar 

  15. Even, J., Pedesseau, L. & Katan, C. Analysis of multivalley and multibandgap absorption and enhancement of free carriers related to exciton screening in hybrid perovskites. J. Phys. Chem. C 118, 11566–11572 (2014).

    Article  Google Scholar 

  16. Yang, Y. et al. Large polarization-dependent exciton optical Stark effect in lead iodide perovskites. Nat. Commun. 7, 12613 (2016).

    Article  ADS  Google Scholar 

  17. Price, M. B. et al. Hot-carrier cooling and photoinduced refractive index changes in organic–inorganic lead halide perovskites. Nat. Commun. 6, 8420 (2015).

    Article  ADS  Google Scholar 

  18. Chen, K., Barker, A. J., Morgan, F. L. C., Halpert, J. E. & Hodgkiss, J. M. Effect of carrier thermalization dynamics on light emission and amplification in organometal halide perovskites. J. Phys. Chem. Lett. 6, 153–158 (2015).

    Article  Google Scholar 

  19. Motta, C. et al. Revealing the role of organic cations in hybrid halide perovskite CH3NH3PbI3 . Nat. Commun. 6, 7026 (2015).

    Article  ADS  Google Scholar 

  20. Yang, Y. et al. Observation of a hot-phonon bottleneck in lead-iodide perovskites. Nat. Photon. 10, 53–59 (2016).

    Article  ADS  Google Scholar 

  21. Manser, J. S. & Kamat, P. V. Band filling with free charge carriers in organometal halide perovskites. Nat. Photon. 8, 737–743 (2014).

    Article  ADS  Google Scholar 

  22. Kuokstis, E. et al. Two mechanisms of blueshift of edge emission in InGaN-based epilayers and multiple quantum wells. Appl. Phys. Lett. 80, 977–979 (2002).

    Article  ADS  Google Scholar 

  23. Peyghambarian, N. 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).

    Article  ADS  Google Scholar 

  24. Wachter, S. et al. Excitation induced shift and broadening of the exciton resonance. Physica B 314, 309–313 (2002).

    Article  ADS  Google Scholar 

  25. Bakulin, A. A. et al. Real-time observation of organic cation reorientation in methylammonium lead iodide perovskites. J. Phys. Chem. Lett. 6, 3663–3669 (2015).

    Article  Google Scholar 

  26. Bublitz, G. U. & Boxer, S. G. Stark spectroscopy: applications in chemistry, biology, and materials science. Annu. Rev. Phys. Chem. 48, 213–242 (1997).

    Article  ADS  Google Scholar 

  27. Grancini, G. et al. Role of microstructure in the electron–hole interaction of hybrid lead halide perovskites. Nat. Photon. 9, 695–701 (2015).

    Article  ADS  Google Scholar 

  28. Valverde-Chavez, D. A. et al. Intrinsic femtosecond charge generation dynamics in single crystal CH3NH3PbI3 . Energy Environ. Sci. 8, 3700–3707 (2015).

    Article  Google Scholar 

  29. Stoumpos, C. C., Malliakas, C. D. & Kanatzidis, M. G. Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near-infrared photoluminescent properties. Inorg. Chem. 52, 9019–9038 (2013).

    Article  Google Scholar 

  30. Soe, C. M. M. et al. Room temperature phase transition in methylammonium lead iodide perovskite thin films induced by hydrohalic acid additives. ChemSusChem 9, 2656–2665 (2016).

    Article  Google Scholar 

Download references

Acknowledgements

E.H. acknowledges support, in part, from the Air Force Office of Scientific Research (FA9550-14-1-0005) and the Packard Foundation (2013-39272). M.K. acknowledges support from the US Department of Energy, Office of Science, Basic Energy Sciences (DE-SC-0012541). The electron microscopy work made use of the EPIC facility of Northwestern University's NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC programme (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation and the State of Illinois (through the IIN). S.N. acknowledges support from the Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry.

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  1. S. Nah and B. Spokoyny: These authors contributed equally to this work

Authors and Affiliations

  1. Department of Chemistry, Northwestern University, Evanston, 60208, Illinois, USA

    S. Nah, B. Spokoyny, C. Stoumpos, C. M. M. Soe, M. Kanatzidis & E. Harel

  2. Argonne-Northwestern Solar Energy Center, Northwestern University, Evanston, 60208, Illinois, USA

    C. M. M. Soe & M. Kanatzidis

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Contributions

S.N., B.S. and E.H. conceived the ideas and designed the experiments. S.N. and B.S. carried out TAM experiments and S.N., B.S. and E.H. analysed the data. C.S. and C.M.M.S. synthesized the perovskite films and performed the XRD and diffuse reflectance measurements under the supervision of M.K. S.N., B.S. and E.H. contributed to writing the paper. All authors discussed the results in the paper.

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Correspondence to E. Harel.

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The authors declare no competing financial interests.

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Nah, S., Spokoyny, B., Stoumpos, C. et al. Spatially segregated free-carrier and exciton populations in individual lead halide perovskite grains. Nature Photon 11, 285–288 (2017). https://doi.org/10.1038/nphoton.2017.36

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