Cation Dynamics in Mixed-Cation (MA)x(FA)1–xPbI3 Hybrid Perovskites from Solid-State NMR

Kubicki, Dominik; Prochowicz, Daniel; Hofstetter, Albert; Péchy, Péter; Zakeeruddin, Shaik M.; Grätzel, Michaël; Emsley, Lyndon

doi:10.1021/jacs.7b04930

Cited by 246 publications

(434 citation statements)

References 51 publications

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“…We have previously shown that solid-state NMR is well suited to probe the atomic-level microstructure of multicomponent lead halide perovskites, [26][27][28][29] yet this approach has not been systematically employed to analyze the structural features of layered 2D perovskites so far. We have previously shown that solid-state NMR is well suited to probe the atomic-level microstructure of multicomponent lead halide perovskites, [26][27][28][29] yet this approach has not been systematically employed to analyze the structural features of layered 2D perovskites so far.…”

Section: Structural Characteristicsmentioning

confidence: 99%

“…[16,26,27] Since the A/FA and A′/FA phases contain a 3D perovskite phase, 14 N MAS NMR can yield information on whether or not this phase is microscopically modified by the presence of the spacer. In the case of 3D perovskites, 14 N MAS NMR spectra feature a spinning sideband (SSB) pattern that corresponds to the central cation reorienting on the picosecond timescale within the cubooctahedral cavity.…”

Section: Structural Characteristicsmentioning

confidence: 99%

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Supramolecular Engineering for Formamidinium‐Based Layered 2D Perovskite Solar Cells: Structural Complexity and Dynamics Revealed by Solid‐State NMR Spectroscopy

Milić

Kubicki

et al. 2019

Advanced Energy Materials

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149

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represent a class of materials described by the general formula S 2 Y n−1 M n X 3n+1 , where S (typically C m H 2m+1 NH 3 + ) and Y (typically methylammonium (MA), formamidinium (FA), or their mixtures) are organic cations, M is a divalent metal cation (Pb 2+ , Sn 2+ ), and X is a halide ion (Br − , I − ). RPPs form layered structures of perovskite-like slabs separated by the organic ammonium cation spacers (S), where the value of n represents the number of layers of [MX 6 ] 4− octahedra in the stack (Figure 1a; n = 1-3). These structural features render the RPPs natural quantum wells where the number of layers in conjunction with the nature of the spacer group determines the optoelectronic properties. [1][2][3] While MA-based layered perovskite compositions have been extensively explored, [3,5,6] reports of FA-based layered perovskites remain scarce despite the better stability of the FA cation. [7][8][9] In addition, unlike their 3D analogues, layered 2D perovskites generally suffer from poor solarto-electric power conversion efficiencies, [1][2][3] particularly for the FA-based layered perovskites reported to date. Despite the ongoing effort, some of the best performing MA-based layered 2D perovskites have exceeded efficiencies of 12% with hotcasting techniques, [3] whereas the present FA-based analogues gave efficiencies around 1% for various compositions, reaching over 6% after extensive treatments. [7][8][9] This relatively poor performance of RPPs can be predominantly attributed to the inhibition of charge transport by the organic cations that act as insulating layers, since it is the inorganic domains that mainly contribute to the conductivity of the system. [1] Moreover, RPPs possess higher exciton binding energies, which result in decreased performance owing to inefficient exciton dissociation, and in turn to short-circuit photocurrent losses. [3,5] This has been counterbalanced by using additives, such as thiourea, [7][8][9] or employing hot-casting fabrication techniques, [1] with limited reproducibility as well as lack of operational stability reports.Here, we consider that these limitations on the performance of RPPs might be overcome by exploiting the potential tunability of the inherent structural properties through the design Perovskite solar cells are one of the most promising photovoltaic technologies, although their molecular level design and stability toward environmental factors remain a challenge. Layered 2D Ruddlesden-Popper perovskite phases feature an organic spacer bilayer that enhances their environmental stability. Here, the concept of supramolecular engineering of 2D perovskite materials is demonstrated in the case of formamidinium (FA) containing A 2 FA n−1 Pb n I 3n+1 formulations by employing (adamantan-1-yl)methanammonium (A) spacers exhibiting propensity for strong Van der Waals interactions complemented by structural adaptability. The molecular design translates into desirable structural features and phases with different compositions and dimensionalities, identified uniquely ...

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Section: Structural Characteristicsmentioning

confidence: 99%

Section: Structural Characteristicsmentioning

confidence: 99%

Supramolecular Engineering for Formamidinium‐Based Layered 2D Perovskite Solar Cells: Structural Complexity and Dynamics Revealed by Solid‐State NMR Spectroscopy

Milić

Kubicki

et al. 2019

Advanced Energy Materials

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149

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“…For each rotation mode about the principal axes of the molecule, the other two rotation angles are fixed (for φ 1 rotations, φ 2 = φ 3 = 0; for φ 2 rotations, φ 1 = (0, 90 29 Reported reorientation times from GHz spectroscopy, quasi-elastic neutron scattering (QENS), ab initio molecular dynamics (MD), and 14 N NMR are presented for comparison. 15,16,23,24,36,42,73 14 reorientation. In particular, it is intriguing to consider if the differing barriers to molecular dipole rotation and differing dipole moments lead to important differences between FAPbI 3 and MAPbI 3 on timescales relevant to exciton dissociation, interaction of charge carriers with polar optical phonons or polarons, or momentum separation of excited electrons and holes due to possible dynamic Rashba-Dresselhaus effects.…”

Section: 41mentioning

confidence: 99%

Universal Dynamics of Molecular Reorientation in Hybrid Lead Iodide Perovskites

et al. 2017

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The role of organic molecular cations in the high-performance perovskite photovoltaic absorbers, methylammonium lead iodide (MAPbI 3 ) and formamidinium lead iodide (FAPbI 3 ), has been an enigmatic subject of great interest. Beyond aiding in the ease of processing of thin films for photovoltaic devices, there have been suggestions that many of the remarkable properties of the halide perovskites can be attributed to the dipolar nature and the dynamic behavior of these cations. Here, we establish the dynamics of the molecular cations in FAPbI 3 between 4 K and 340 K and the nature of their interaction with the surrounding inorganic cage using a combination of solid state nuclear magnetic resonance and dielectric spectroscopies, neutron scattering, calorimetry, and ab initio calculations. Detailed comparisons of the reported temperature dependence of the dynamics of MAPbI 3 are then carried out which reveal the molecular ions in the two different compounds to exhibit very similar rotation rates (≈8 ps) at room temperature, despite differences in other temperature regimes.For FA, rotation about the N···N axis, which reorients the molecular dipole, is the dominant motion in all phases, with an activation barrier of ≈21 meV in the ambient phase, compared to ≈110 meV for the analogous dipole reorientation of MA. Geometrical frustration of the molecule-cage interaction in FAPbI 3 produces a disordered γ-phase and subsequent glassy freezing at yet lower temperatures. Hydrogen bonds suggested by atom-atom distances from neutron total scattering experiments imply a substantial role for the molecules in directing structure and dictating properties. The temperature dependence of reorientation of the dipolar molecular cations systematically described here can clarify various hypotheses including large-polaron charge transport and fugitive electron spin polarization that have been invoked in the context of these unusual materials.2

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“…Our group has very recently used solid-state NMR to elucidate microscopic phase composition and segregation in MA/FA HOPs. 26 …”

Section: Introductionmentioning

confidence: 99%

Phase Segregation in Cs-, Rb- and K-Doped Mixed-Cation (MA)_x(FA)_1–xPbI₃ Hybrid Perovskites from Solid-State NMR

Kubicki¹,

Prochowicz

Hofstetter³

et al. 2017

J. Am. Chem. Soc.

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340

445

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Hybrid (organic–inorganic) multication lead halide perovskites hold promise for a new generation of easily processable solar cells. Best performing compositions to date are multiple-cation solid alloys of formamidinium (FA), methylammonium (MA), cesium, and rubidium lead halides which provide power conversion efficiencies up to around 22%. Here, we elucidate the atomic-level nature of Cs and Rb incorporation into the perovskite lattice of FA-based materials. We use 133Cs, 87Rb, 39K, 13C, and 14N solid-state MAS NMR to probe microscopic composition of Cs-, Rb-, K-, MA-, and FA-containing phases in double-, triple-, and quadruple-cation lead halides in bulk and in a thin film. Contrary to previous reports, we have found no proof of Rb or K incorporation into the 3D perovskite lattice in these systems. We also show that the structure of bulk mechanochemical perovskites bears close resemblance to that of thin films, making them a good benchmark for structural studies. These findings provide fundamental understanding of previously reported excellent photovoltaic parameters in these systems and their superior stability.

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Cation Dynamics in Mixed-Cation (MA)_x(FA)_1–xPbI₃ Hybrid Perovskites from Solid-State NMR

Cited by 246 publications

References 51 publications

Supramolecular Engineering for Formamidinium‐Based Layered 2D Perovskite Solar Cells: Structural Complexity and Dynamics Revealed by Solid‐State NMR Spectroscopy

Supramolecular Engineering for Formamidinium‐Based Layered 2D Perovskite Solar Cells: Structural Complexity and Dynamics Revealed by Solid‐State NMR Spectroscopy

Universal Dynamics of Molecular Reorientation in Hybrid Lead Iodide Perovskites

Phase Segregation in Cs-, Rb- and K-Doped Mixed-Cation (MA)_x(FA)_1–xPbI₃ Hybrid Perovskites from Solid-State NMR

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Cation Dynamics in Mixed-Cation (MA)x(FA)1–xPbI3 Hybrid Perovskites from Solid-State NMR

Cited by 246 publications

References 51 publications

Supramolecular Engineering for Formamidinium‐Based Layered 2D Perovskite Solar Cells: Structural Complexity and Dynamics Revealed by Solid‐State NMR Spectroscopy

Supramolecular Engineering for Formamidinium‐Based Layered 2D Perovskite Solar Cells: Structural Complexity and Dynamics Revealed by Solid‐State NMR Spectroscopy

Universal Dynamics of Molecular Reorientation in Hybrid Lead Iodide Perovskites

Phase Segregation in Cs-, Rb- and K-Doped Mixed-Cation (MA)x(FA)1–xPbI3 Hybrid Perovskites from Solid-State NMR

Contact Info

Product

Resources

About

Cation Dynamics in Mixed-Cation (MA)_x(FA)_1–xPbI₃ Hybrid Perovskites from Solid-State NMR

Phase Segregation in Cs-, Rb- and K-Doped Mixed-Cation (MA)_x(FA)_1–xPbI₃ Hybrid Perovskites from Solid-State NMR