Quantitative Phase-Change Thermodynamics and Metastability of Perovskite-Phase Cesium Lead Iodide

Dastidar, Subham; Hawley, Christopher J.; Dillon, Andrew D.; Gutierrez-Perez, Alejandro; Spanier, Jonathan E.; Fafarman, Aaron T.

doi:10.1021/acs.jpclett.7b00134

Cited by 211 publications

(246 citation statements)

References 29 publications

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“…[51] We observe this as well (by comparing the SNR of normalized spectra), along with slight shifts in the luminescence maximum. [75][76] These results are similar to recent reports showing TGA measurements of CsPbI 3 , [74] CsPbBr 3 , [77] and Mn 2 + -doped CsPbCl 3 . For CsPbBr 3 and CsPbI 3 , slight blue shifts are observed with heating, however, CsPbBr 3 does not shift back upon cooling, indicating an irreversible process occurred.…”

Section: Thermal Stability Of Cspbx 3 Nanocrystalssupporting

confidence: 91%

“…In an effort to elucidate the thermal stability and compare to the photostability data of these nanocrystals, thermal stability measurements were performed. [74] Compared to the samples studied by Liao et al wherein no crystal growth was reported, our CsPbI 3 and CsPbI 3 -MeOAc samples underwent phase changes at lower temperatures and exhibited crystal growth. The XRD patterns for the CsPbX 3 perovskite nanocrystals after heating are shown in Figure 6.…”

Section: Thermal Stability Of Cspbx 3 Nanocrystalscontrasting

confidence: 60%

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Unveiling the Photo‐ and Thermal‐Stability of Cesium Lead Halide Perovskite Nanocrystals

et al. 2019

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Lead halide perovskites possess unique characteristics that are well-suited for optoelectronic and energy capture devices, however, concerns about their long-term stability remain. Limited stability is often linked to the methylammonium cation, and all-inorganic CsPbX 3 (X=Cl, Br, I) perovskite nanocrystals have been reported with improved stability. In this work, the photostability and thermal stability properties of CsPbX 3 (X=Cl, Br, I) nanocrystals were investigated by means of electron microscopy, X-ray diffraction, thermogravimetric analysis coupled with FTIR (TGA-FTIR), ensemble and single particle spectral characterization. CsPbBr 3 was found to be stable under 1-sun illumination for 16 h in ambient conditions, although single crystal luminescence analysis after illumination using a solar simulator indicates that the luminescence states are changing over time. CsPbBr 3 was also stable to heating to 250°C. Large CsPbI 3 crystals (34 � 5 nm) were shown to be the least stable composition under the same conditions as both XRD reflections and Raman bands diminish under irradiation; and with heating the γ (black) phase reverts to the nonluminescent δ phase. Smaller CsPbI 3 nanocrystals (14 � 2 nm) purified by a different washing strategy exhibited improved photostability with no evidence of crystal growth but were still thermally unstable. Both CsPbCl 3 and CsPbBr 3 show crystal growth under irradiation or heat, likely with a preferential orientation based on XRD patterns. TGA-FTIR revealed nanocrystal mass loss was only from liberation and subsequent degradation of surface ligands. Encapsulation or other protective strategies should be employed for long-term stability of these materials under conditions of high irradiance or temperature.[a] B.

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Section: Thermal Stability Of Cspbx 3 Nanocrystalssupporting

confidence: 91%

Section: Thermal Stability Of Cspbx 3 Nanocrystalscontrasting

confidence: 60%

Unveiling the Photo‐ and Thermal‐Stability of Cesium Lead Halide Perovskite Nanocrystals

et al. 2019

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“…While the authors claim that rapid cooling of the high-temperature cubic phase preserves the disorder that provides short-term stabilization of α-FAPbI 3 , the same is observed for all-inorganic α-CsPbI 3 , which is also unstable toward the photoinactive δ-phase with double chains of face-shared PbI 6 octahedral units. [19,20] Our results show that the α-δ-phase transition of FAPbI 3 is related to the flexibility of the lead iodine skeleton (see ref. [21] and references therein), specifically the low-temperature PbI 6 tilting and rotational modes associated with halogen I···I bond formation.…”

Section: Introductionmentioning

confidence: 64%

Suppressing X‐Migrations and Enhancing the Phase Stability of Cubic FAPbX₃ (X = Br, I)

Oranskaia

Schwingenschlögl

2019

Advanced Energy Materials

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10 4 cm −1 in the visible-to-infrared region, bandgaps of 1.4-2.3 eV depending on A and X, form Wannier excitons of hundreds of Å diameter and tens of meV binding energy, and have high charge carrier diffusion lengths of up to µm. [1][2][3][4] The highest certified perovskite solar cell power conversion efficiency rapidly increased from 3.8% in 2009 to 22.1% in 2016 using hybrid FAPbI 3 doped with 5% MAPbBr 3[5] (and now stands at 24.2% [6] ). MA and FA stand for methylammonium and formamidinium, light polar organic cations formed by the simplest protonated amine NH 2 CH 3 and amidine NH 2 CHNH. Being incorporated into the lead halide crystal lattice, these organic cations participate not only in strong electrostatic and van der Waals interactions with the inorganic skeleton but also in hydrogen H···X bonding between H atoms (organic cation) and X atoms (inorganic skeleton) that is absent in all-inorganic perovskites. Being an electrondeficient π-conjugated system, FA also participates in π-anion π···X bonding with X atoms. [7] Though the organic cations do not directly determine the optoelectronic properties of hybrid perovskites, they do stabilize the inorganic skeleton of "3D" α-FAPbX 3 (cubic phase) and determine its defect properties, especially regarding X-defects. Goal of the present study therefore is to investigate the role of the FA bonding properties in α-FAPbX 3 and to propose promising organic cation doping strategies.The rising star of hybrid perovskite field of solar energy harvesting, α-FAPbI 3 , has a narrower bandgap than well-studied β-MAPbI 3 (tetragonal phase) and, more importantly, is more stable against decomposition and degradation. [8][9][10][11][12][13] Despite many advantages, β-MAPbI 3 has the serious problem that it is intrinsically thermodynamically unstable, decomposing into PbI 2 and MAI (and further into volatile amine and HI), and readily degrades even at moderate operating temperatures when exposed to water and/or oxygen. Lower affinity of α-FAPbI 3 to decomposition and degradation is related to weaker acidity (as a result of aromatic stabilization), larger volume, and stronger bonding with the halides of FA than MA, which manifests in experiment as suppressed hysteresis due to I-migrations. [5,14] The mobile I-defects in β-MAPbI 3 are detrimental not only to the structural stability of the material but also to its charge transport properties when acting as electron-hole recombination centers. [15][16][17] In this respect, it is crucial to understand the influence of FA on the X-migrations in α-FAPbX 3 and to identify ways to manipulate them by introducing stronger bonding organic cations as dopants.Chemical bonding of formamidinium (FA) with the inorganic perovskite skeleton of FAPbX 3 (X = Br, I) is studied with emphasis on the differences to methylammonium: stronger hydrogen bonding, the presence of π-anion bonding, and more sterically hindered motion inside the perovskite inorganic cage. Organic cation dopants fitting in the perovskite cubic cell and being capable of hydroge...

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“…As the pore sizes of AAO templates decreased below 41 nm, the intensity of the absorption band edge at ≈720 nm significantly increased owing to the presence of the black α-phase, whereas the absorption peak near 420 nm completely vanished because of the absence of the yellow δ-phase. [18,24,28,41] By contrast, in the case of CsPbI 3 grown inside the 56, 69, and 112 nm pore sized AAO templates, the absorption peak at ≈420 nm indicative of the existence of the yellow δ-phase was clearly observed. The pore size-dependent absorption spectra variation demonstrated that the degree of spatial confinement induced by different pore sizes enables manipulation of the phase stability of CsPbI 3 , which is consistent with our XRD results.…”

Section: Resultsmentioning

confidence: 99%

Strain‐Mediated Phase Stabilization: A New Strategy for Ultrastable α‐CsPbI₃ Perovskite by Nanoconfined Growth

Kim

Jeong

et al. 2019

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All‐inorganic cesium lead triiodide (CsPbI3) perovskite is considered a promising solution‐processable semiconductor for highly stable optoelectronic and photovoltaic applications. However, despite its excellent optoelectronic properties, the phase instability of CsPbI3 poses a critical hurdle for practical application. In this study, a novel stain‐mediated phase stabilization strategy is demonstrated to significantly enhance the phase stability of cubic α‐phase CsPbI3. Careful control of the degree of spatial confinement induced by anodized aluminum oxide (AAO) templates with varying pore sizes leads to effective manipulation of the phase stability of α‐CsPbI3. The Williamson–Hall method in conjunction with density functional theory calculations clearly confirms that the strain imposed on the perovskite lattice when confined in vertically aligned nanopores can alter the formation energy of the system, stabilizing α‐CsPbI3 at room temperature. Finally, the CsPbI3 grown inside nanoporous AAO templates exhibits exceptional phase stability over three months under ambient conditions, in which the resulting light‐emitting diode reveals a natural red color emission with very narrow bandwidth (full width at half maximum of 33 nm) at 702 nm. The universally applicable template‐based stabilization strategy can give in‐depth insights on the strain‐mediated phase transition mechanism in all‐inorganic perovskites.

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Quantitative Phase-Change Thermodynamics and Metastability of Perovskite-Phase Cesium Lead Iodide

Cited by 211 publications

References 29 publications

Unveiling the Photo‐ and Thermal‐Stability of Cesium Lead Halide Perovskite Nanocrystals

Unveiling the Photo‐ and Thermal‐Stability of Cesium Lead Halide Perovskite Nanocrystals

Suppressing X‐Migrations and Enhancing the Phase Stability of Cubic FAPbX₃ (X = Br, I)

Strain‐Mediated Phase Stabilization: A New Strategy for Ultrastable α‐CsPbI₃ Perovskite by Nanoconfined Growth

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Quantitative Phase-Change Thermodynamics and Metastability of Perovskite-Phase Cesium Lead Iodide

Cited by 211 publications

References 29 publications

Unveiling the Photo‐ and Thermal‐Stability of Cesium Lead Halide Perovskite Nanocrystals

Unveiling the Photo‐ and Thermal‐Stability of Cesium Lead Halide Perovskite Nanocrystals

Suppressing X‐Migrations and Enhancing the Phase Stability of Cubic FAPbX3 (X = Br, I)

Strain‐Mediated Phase Stabilization: A New Strategy for Ultrastable α‐CsPbI3 Perovskite by Nanoconfined Growth

Contact Info

Product

Resources

About

Suppressing X‐Migrations and Enhancing the Phase Stability of Cubic FAPbX₃ (X = Br, I)

Strain‐Mediated Phase Stabilization: A New Strategy for Ultrastable α‐CsPbI₃ Perovskite by Nanoconfined Growth