Origins of the long-range exciton diffusion in perovskite nanocrystal films: photon recycling vs exciton hopping

AbstractThe outstanding optoelectronic performance of lead halide perovskites lies in their exceptional carrier diffusion properties. As the perovskite material dimensionality is reduced to exploit the quantum confinement effects, the disruption to the perovskite lattice, often with insulating organic ligands, raises new questions on the charge diffusion properties. Herein, we report direct imaging of >1 μm exciton diffusion lengths in CH3NH3PbBr3 perovskite nanocrystal (PNC) films. Surprisingly, the resulting exciton mobilities in these PNC films can reach 10 ± 2 cm2 V−1 s−1, which is counterintuitively several times higher than the carrier mobility in 3D perovskite films. We show that this ultralong exciton diffusion originates from both efficient inter-NC exciton hopping (via Förster energy transfer) and the photon recycling process with a smaller yet significant contribution. Importantly, our study not only sheds new light on the highly debated origins of the excellent exciton diffusion in PNC films but also highlights the potential of PNCs for optoelectronic applications.

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Atomic-scale microstructure of metal halide perovskite

Science ◽

10.1126/science.abb5940 ◽

2020 ◽

Vol 370 (6516) ◽

pp. eabb5940 ◽

Cited By ~ 1

Author(s):

Mathias Uller Rothmann ◽

Judy S. Kim ◽

Juliane Borchert ◽

Kilian B. Lohmann ◽

Colum M. O’Leary ◽

...

Keyword(s):

Scanning Transmission Electron Microscopy ◽

Atomic Scale ◽

Energy Applications ◽

Transmission Electron ◽

Metal Halide Perovskite ◽

Scanning Transmission ◽

Halide Perovskites ◽

Crystalline Solar Cell ◽

Lead Halide ◽

Perovskite Lattice

Hybrid organic-inorganic perovskites have high potential as materials for solar energy applications, but their microscopic properties are still not well understood. Atomic-resolution scanning transmission electron microscopy has provided invaluable insights for many crystalline solar cell materials, and we used this method to successfully image formamidinium lead triiodide [CH(NH2)2PbI3] thin films with a low dose of electron irradiation. Such images reveal a highly ordered atomic arrangement of sharp grain boundaries and coherent perovskite/PbI2 interfaces, with a striking absence of long-range disorder in the crystal. We found that beam-induced degradation of the perovskite leads to an initial loss of formamidinium [CH(NH2)2+] ions, leaving behind a partially unoccupied perovskite lattice, which explains the unusual regenerative properties of these materials. We further observed aligned point defects and climb-dissociated dislocations. Our findings thus provide an atomic-level understanding of technologically important lead halide perovskites.

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Enhancing photoluminescence yields in lead halide perovskites by photon recycling and light out-coupling

Nature Communications ◽

10.1038/ncomms13941 ◽

2016 ◽

Vol 7 (1) ◽

Cited By ~ 218

Author(s):

Johannes M. Richter ◽

Mojtaba Abdi-Jalebi ◽

Aditya Sadhanala ◽

Maxim Tabachnyk ◽

Jasmine P.H. Rivett ◽

...

Keyword(s):

Halide Perovskites ◽

Photon Recycling ◽

Lead Halide

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Decoding ultrafast polarization responses in lead halide perovskites by the two-dimensional optical Kerr effect

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2022268118 ◽

2021 ◽

Vol 118 (7) ◽

pp. e2022268118

Author(s):

Sebastian F. Maehrlein ◽

Prakriti P. Joshi ◽

Lucas Huber ◽

Feifan Wang ◽

Marie Cherasse ◽

...

Keyword(s):

Kerr Effect ◽

Light Propagation ◽

Incident Light ◽

Stimulated Emission ◽

Optical Kerr Effect ◽

Two Dimensional ◽

Polarization Response ◽

Halide Perovskites ◽

Photon Recycling ◽

Lead Halide

The ultrafast polarization response to incident light and ensuing exciton/carrier generation are essential to outstanding optoelectronic properties of lead halide perovskites (LHPs). A large number of mechanistic studies in the LHP field to date have focused on contributions to polarizability from organic cations and the highly polarizable inorganic lattice. For a comprehensive understanding of the ultrafast polarization response, we must additionally account for the nearly instantaneous hyperpolarizability response to the propagating light field itself. While light propagation is pivotal to optoelectronics and photonics, little is known about this in LHPs in the vicinity of the bandgap where stimulated emission, polariton condensation, superfluorescence, and photon recycling may take place. Here we develop two-dimensional optical Kerr effect (2D-OKE) spectroscopy to energetically dissect broadband light propagation and dispersive nonlinear polarization responses in LHPs. In contrast to earlier interpretations, the below-bandgap OKE responses in both hybrid CH3NH3PbBr3 and all-inorganic CsPbBr3 perovskites are found to originate from strong hyperpolarizability and highly anisotropic dispersions. In both materials, the nonlinear mixing of anisotropically propagating light fields results in convoluted oscillatory polarization dynamics. Based on a four-wave mixing model, we quantitatively derive dispersion anisotropies, reproduce 2D-OKE frequency correlations, and establish polarization-dressed light propagation in single-crystal LHPs. Moreover, our findings highlight the importance of distinguishing the often-neglected anisotropic light propagation from underlying coherent quasiparticle responses in various forms of ultrafast spectroscopy.

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Photon Recycling by Energy Transfer in Piezochemically Synthesized and Close-Packed Methylammonium Lead Halide Perovskites

The Journal of Physical Chemistry C ◽

10.1021/acs.jpcc.9b07003 ◽

2019 ◽

Vol 123 (45) ◽

pp. 27752-27758 ◽

Cited By ~ 5

Author(s):

Sushant Ghimire ◽

Kiyonori Takahashi ◽

Yuta Takano ◽

Takayoshi Nakamura ◽

Vasudevanpillai Biju

Keyword(s):

Energy Transfer ◽

Halide Perovskites ◽

Photon Recycling ◽

Lead Halide

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Local Morphology Effects on the Photoluminescence Properties of Thin CsPbBr3 Nanocrystal Films

Nanomaterials ◽

10.3390/nano11061470 ◽

2021 ◽

Vol 11 (6) ◽

pp. 1470

Author(s):

Marco Anni ◽

Arianna Cretí ◽

Maria Luisa De De Giorgi ◽

Mauro Lomascolo

Keyword(s):

Deep Understanding ◽

Photonic Devices ◽

Photoluminescence Properties ◽

Active Materials ◽

Emission Properties ◽

Morphological Variations ◽

Nanocrystal Films ◽

Halide Perovskites ◽

Extreme Care ◽

Lead Halide

Lead halide perovskites are emerging as extremely interesting active materials for a wide variety of optoelectronic and photonic devices. A deep understanding of their photophysics is thus fundamental in order to properly understand the origins of the materials active properties and to provide strategies for improving them. In this work, we exploit the local morphological variations in a drop-cast thin CsPbBr3 nanocrystal film to show that the aggregation of NCs has strong effects on the peak wavelengths of PL spectra, the linewidth, and the intensity of dependence on temperature. An analysis based on models that are frequently used in the literature led to completely different conclusions about the intrinsic NC emission properties extracted from spectra measured in points with different contribution of the PL from the aggregates. Our results demonstrate that extreme care has to be used in order to correctly correlate the spectral PL features with the intrinsic emission properties of lead halide perovskite NC films.

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