Atomistic origin of lattice softness and its impact on structural and carrier dynamics in three dimensional perovskites

Guo, Zhang; Wang, Jing; Yin, Wan‐Jian

doi:10.1039/d1ee02131a

Cited by 29 publications

(25 citation statements)

References 131 publications

(147 reference statements)

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“…Raman data recorded at 80 K also show that the energy of the lattice modes decreases in the order FAPbBr 3 > MAPbBr 3 > MHyPbBr 3 (the lowest wavenumber mode decreases from 32 cm –1 for FAPbBr 3 to 24 cm –1 for MAPbBr 3 and 22 cm –1 for MHyPbBr 3 ). The presence of such low-wavenumber optical modes is consistent with high lattice softness of these perovskites, i.e., their low bulk moduli and high compressibility. ,, It is also clear that MHyPbBr 3 shows larger number of lattice modes than the FA and MA analogues. This behavior reflects much more pronounced distortion of the Pb–Br framework in case of the MHy analogue, compared to the FA and MA counterparts.…”

Section: Discussionsupporting

confidence: 54%

“…The presence of such low-wavenumber optical modes is consistent with high lattice softness of these perovskites, i.e., their low bulk moduli and high compressibility. 40,50,51 It is also clear that MHyPbBr 3 shows larger number of lattice modes than the FA and MA analogues. This behavior reflects much more pronounced distortion of the Pb− Br framework in case of the MHy analogue, compared to the FA and MA counterparts.…”

Section: ■ Discussionmentioning

confidence: 96%

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Comparative Studies of Phonon Properties of Three-Dimensional Hybrid Organic–Inorganic Perovskites Comprising Methylhydrazinium, Methylammonium, and Formamidinium Cations

2022

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Three-dimensional hybrid organic–inorganic perovskites with halide, formate, or hypophosphite ligands are promising photovoltaic, light-emitting, and multiferroic materials. Since the properties of these compounds are strongly affected by changes in lattice dynamics, it is of great importance to understand their phonon properties. We report Raman and IR spectra for a number of perovskites to understand the effect of various metal-linker frameworks on vibrations of methylhydrazinium, formamidinium, and methylammonium cations as well as effects of these cations on lattice phonons in lead bromide analogues. Our results show that the lattice dynamics and energy of lattice phonons of lead halides depend strongly on the type of organic cation and temperature. In particular, at room temperature, the dynamics of methylhydrazinium cations is much slower compared to the dynamics of methylammonium and formamidinium cations, implying weaker electron scattering in the former case and thus significantly different optoelectronic properties compared to the formamidinium and methylammonium analogues. We also show that the size of the halide ion affects the energy of internal modes, but this effect is much more pronounced when halide ligands are replaced by formate or hypophosphite anions, especially in the case of formamidinium analogues. We attribute this behavior to strong variation of hydrogen bond strength and changes in the internal structure of organic cations.

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Section: Discussionsupporting

confidence: 54%

Section: ■ Discussionmentioning

confidence: 96%

Comparative Studies of Phonon Properties of Three-Dimensional Hybrid Organic–Inorganic Perovskites Comprising Methylhydrazinium, Methylammonium, and Formamidinium Cations

2022

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“…In both cases, the highest modulation depth is observed at W-band frequency. Slightly lower measured values point to a distribution of the tunneling frequency caused by different methyl group environments, which may originate from the structural defects [ 45 ] and local deformations due to the soft nature of the hybrid perovskite [ 46 ].…”

Section: Results and Discussionmentioning

confidence: 99%

Probing Methyl Group Tunneling in [(CH3)2NH2][Zn(HCOO)3] Hybrid Perovskite Using Co2+ EPR

et al. 2023

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At low temperature, methyl groups act as hindered quantum rotors exhibiting rotational quantum tunneling, which is highly sensitive to a local methyl group environment. Recently, we observed this effect using pulsed electron paramagnetic resonance (EPR) in two dimethylammonium-containing hybrid perovskites doped with paramagnetic Mn2+ ions. Here, we investigate the feasibility of using an alternative fast-relaxing Co2+ paramagnetic center to study the methyl group tunneling, and, as a model compound, we use dimethylammonium zinc formate [(CH3)2NH2][Zn(HCOO)3] hybrid perovskite. Our multifrequency (X-, Q- and W-band) EPR experiments reveal a high-spin state of the incorporated Co2+ center, which exhibits fast spin-lattice relaxation and electron spin decoherence. Our pulsed EPR experiments reveal magnetic field independent electron spin echo envelope modulation (ESEEM) signals, which are assigned to the methyl group tunneling. We use density operator simulations to extract the tunnel frequency of 1.84 MHz from the experimental data, which is then used to calculate the rotational barrier of the methyl groups. We compare our results with the previously reported Mn2+ case showing that our approach can detect very small changes in the local methyl group environment in hybrid perovskites and related materials.

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“…Considerable efforts have been dedicated to establish the origin of anharmonicity in hybrid perovskites. 56,[59][60][61][62][63] It has been shown that the vibrational anharmonicity in MHPs is associated with the displacement of halogen atoms perpendicular to the Pb-X-Pb bonding axis. 64,65 Ab initio MD simulations can naturally account for temperature and anharmonic effects in materials, offering an opportunity to directly explore anharmonicity of atomic vibrations.…”

Section: −mentioning

confidence: 99%

Interplay of structural fluctuations and charge carrier dynamics is key for high performance of hybrid lead halide perovskites

Zhan

Xie

Prezhdo

et al. 2022

Inorg. Chem. Front.

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Atomistic origin of lattice softness and its impact on structural and carrier dynamics in three dimensional perovskites

Abstract: The soft lattices of lead-halide perovskites (LHPs) are responsible for their unique material properties, including polaron formation, defect tolerance, anharmonic vibration, and large electrostrictive response, which result in exotic carrier...

Cited by 29 publications

References 131 publications

Comparative Studies of Phonon Properties of Three-Dimensional Hybrid Organic–Inorganic Perovskites Comprising Methylhydrazinium, Methylammonium, and Formamidinium Cations

Comparative Studies of Phonon Properties of Three-Dimensional Hybrid Organic–Inorganic Perovskites Comprising Methylhydrazinium, Methylammonium, and Formamidinium Cations

Probing Methyl Group Tunneling in [(CH3)2NH2][Zn(HCOO)3] Hybrid Perovskite Using Co2+ EPR

Interplay of structural fluctuations and charge carrier dynamics is key for high performance of hybrid lead halide perovskites

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