Vibrational spectra of methylammonium iodide and formamidinium iodide in a wide temperature range

Bukleski, Miha; Dimitrovska-Lazova, Sandra; Aleksovska, Slobotka

doi:10.20450/mjcce.2019.1940

Cited by 15 publications

(15 citation statements)

References 29 publications

(58 reference statements)

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“…[24] Peak positions and assignments for FAI and FABr are shown in Table S2, Supporting Information, and are consistent with previous reports. [23,24] The appearance of asymmetric NH 2 stretching vibrations >3000 cm À1 , and the NCN stretch at %1690 cm À1 , confirms the formation of the formamidinium salt. The FABr spectrum is nearly identical to that of FAI with strong absorptions of NH 2 > 3000 cm À1 and NCN % 1700 cm À1 which confirm its structure.…”

Section: Atr-ftir Spectroscopymentioning

confidence: 80%

“…For FAI synthesis, [23] 19.7 g formamidinium acetate (Sigma Aldrich), was added to a beaker of 50 mL HI at 0 C under argon and stirred for 2 h. Solutions were then dried at T < 50 C. The resulting white solids were recrystallized from ethanol twice at T < 50 C and rinsed well with diethyl ether. Moderate temperatures were used during the purification steps to avoid decomposition of the FAþ ion to NH 3 /NH þ 4 .…”

Section: Methodsmentioning

confidence: 99%

“…The measured peaks for each CH 3 , C-N, and NH 3 mode are consistent with previous reports and confirm the synthesis of MAI and MABr. [21,23] Notably, the MABr peaks are shifted toward higher wavenumber than the MAI peaks, likely due to different hydrogen bonding interactions between the halides. [24] Peak positions and assignments for FAI and FABr are shown in Table S2, Supporting Information, and are consistent with previous reports.…”

Section: Atr-ftir Spectroscopymentioning

confidence: 99%

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Thermal and Structural Characterization of Methylammonium‐ and Formamidinium‐Halide Salts

Harding

Dobson

Ogunnaike

et al. 2021

Physica Status Solidi (a)

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Four organic halide salts of interest to alloyed perovskite solar cell fabrication are characterized using attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR), powder X‐ray diffraction (XRD), and thermogravimetric analysis. The chemical and crystal structures of methylammonium iodide (MAI), methylammonium bromide (MABr), and formamidinium iodide (FAI) are confirmed, and the experimental ATR‐FTIR spectrum and XRD pattern of formamidinium bromide (FABr) are presented. The enthalpy, ΔH vap, and entropy, ΔS vap, of vaporization are quantified for each salt and are used to estimate their vapor pressures in the temperature range of 150–300 °C. MAI, MABr, and FAI have similar vapor pressures in this temperature range, whereas FABr has a higher vapor pressure in the temperature range of 150–240 °C. These data provide a foundation for achieving effective control of vapor phase concentrations for vapor processing of alloyed perovskite solar cells.

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Section: Atr-ftir Spectroscopymentioning

confidence: 80%

Section: Methodsmentioning

confidence: 99%

Section: Atr-ftir Spectroscopymentioning

confidence: 99%

See 1 more Smart Citation

Thermal and Structural Characterization of Methylammonium‐ and Formamidinium‐Halide Salts

Harding

Dobson

Ogunnaike

et al. 2021

Physica Status Solidi (a)

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“…The approach was proven for the salts FAI and MAI, whose hydrogen bonds are known to exist at −180 °C. 29,30 ■ METHODS Sample Preparation. Single crystals (SCs) of MAPbI 3 , MAPbBr 3 , FAPbBr 3 , and FAPbI 3 were synthesized by the modified inverse temperature crystallization method.…”

Section: ■ Introductionmentioning

confidence: 99%

Do Lead Halide Hybrid Perovskites Have Hydrogen Bonds?

et al. 2022

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Hydrogen bonds impact many material properties due to the bond directionality and collective strength. For them to exist, the atoms connected to hydrogen should possess high electronegativity, the distance between the interacting atoms should be less than their van der Waals radii, and there should be a charge transfer between them. In hybrid perovskites, the impact of hydrogen bonds is ascribed to several phenomena. Among them are the effect of passivation at the surface, structural stability of the mixed cation compounds, structural instability of FAPbI3, and ferroelectric behavior. In this paper, we applied a deterministic method to prove the existence of hydrogen bonds using Raman spectroscopy. This approach was successfully applied to water and is based on the emergence of a Raman mode as a result of the intermolecular charge transfer, which is not measured for the isolated molecule. With the help of DFT calculations, we attributed the Raman modes detected at room temperature (RT) for MAI and FAI and compared them with the Raman spectra of MAPbX3 and FAPbX3. This comparison has shown that there are no hydrogen bonds in hybrid lead halide perovskites at RT.

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“…We note that the existing literature on MAX and FAX is mainly devoted to structural, vibrational, and thermodynamic properties − but lacks information about their electronic structures (which is crucial for an optimization of associated LHPs). Thus, in the present study, we carry out a detailed investigation of the nitrogen and carbon K-edge XE spectra of the LHP precursor materials MAX (X = Cl, I) and FAX (X = Br, I), in combination with density functional theory (DFT) electronic structure calculations.…”

Section: Introductionmentioning

confidence: 99%

Coupling Methylammonium and Formamidinium Cations with Halide Anions: Hybrid Orbitals, Hydrogen Bonding, and the Role of Dynamics

et al. 2021

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The electronic structures of four precursors for organic–inorganic hybrid perovskites, namely, methylammonium chloride and iodide, as well as formamidinium bromide and iodide, are investigated by X-ray emission (XE) spectroscopy at the carbon and nitrogen K-edges. The XE spectra are analyzed based on density functional theory calculations. We simulate the XE spectra at the Kohn–Sham level for ground-state geometries and carry out detailed analyses of the molecular orbitals and the electronic density of states to give a thorough understanding of the spectra. Major parts of the spectra can be described by the model of the corresponding isolated organic cation, whereas high-emission energy peaks in the nitrogen K-edge XE spectra arise from electronic transitions involving hybrids of the molecular and atomic orbitals of the cations and halides, respectively. We find that the interaction of the methylammonium cation is stronger with the chlorine than with the iodine anion. Furthermore, our detailed theoretical analysis highlights the strong influence of ultrafast proton dynamics in the core-excited states, which is an intrinsic effect of the XE process. The inclusion of this effect is necessary for an accurate description of the experimental nitrogen K-edge X-ray emission spectra and gives information on the hydrogen-bonding strengths in the different precursor materials.

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Vibrational spectra of methylammonium iodide and formamidinium iodide in a wide temperature range

Cited by 15 publications

References 29 publications

Thermal and Structural Characterization of Methylammonium‐ and Formamidinium‐Halide Salts

Thermal and Structural Characterization of Methylammonium‐ and Formamidinium‐Halide Salts

Do Lead Halide Hybrid Perovskites Have Hydrogen Bonds?

Coupling Methylammonium and Formamidinium Cations with Halide Anions: Hybrid Orbitals, Hydrogen Bonding, and the Role of Dynamics

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