Collective Molecular Mechanisms in the CH3NH3PbI3 Dissolution by Liquid Water

Caddeo, Claudia; Saba, Maria Ilenia; Meloni, Simone; Filippetti, Alessio; Mattoni, Alessandro

doi:10.1021/acsnano.7b04116

Cited by 84 publications

(99 citation statements)

References 74 publications

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“…Classical molecular dynamics (MD) makes it possible to simulate large‐scale models of MAPbI 3 including point‐defects and GBs. Interatomic forces of MAPbI 3 can be modeled by the MYP force field developed by Mattoni et al [ 49,50 ] which have been successfully applied to study vibrations and thermodynamic properties of MAPbI 3 , degradation in water [ 51,52 ] as well as diffusion of point‐defects. [ 6 ] Here, we apply MD to simulate the diffusion of one iodine vacancy (i.e., the most mobile point defect in MAPbI 3 [ 6 ] ) in presence of the Σ5/(102) grain boundary, i.e., a prototypical boundary in MAPbI 3 forming along the (102) crystallographic plane with 53.1° tilt angle.…”

Section: Resultsmentioning

confidence: 99%

The Role of Grain Boundaries on Ionic Defect Migration in Metal Halide Perovskites

Phung

Al‐Ashouri

Meloni

et al. 2020

Advanced Energy Materials

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144

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Halide perovskites are emerging as revolutionary materials for optoelectronics. Their ionic nature and the presence of mobile ionic defects within the crystal structure have a dramatic influence on the operation of thin‐film devices such as solar cells, light‐emitting diodes, and transistors. Thin films are often polycrystalline and it is still under debate how grain boundaries affect the migration of ions and corresponding ionic defects. Laser excitation during photoluminescence (PL) microscopy experiments leads to formation and subsequent migration of ionic defects, which affects the dynamics of charge carrier recombination. From the microscopic observation of lateral PL distribution, the change in the distribution of ionic defects over time can be inferred. Resolving the PL dynamics in time and space of single crystals and thin films with different grain sizes thus, provides crucial information about the influence of grain boundaries on the ionic defect movement. In conjunction with experimental observations, atomistic simulations show that defects are trapped at the grain boundaries, thus inhibiting their diffusion. Hence, with this study, a comprehensive picture highlighting a fundamental property of the material is provided while also setting a theoretical framework in which the interaction between grain boundaries and ionic defect migration can be understood.

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Section: Resultsmentioning

confidence: 99%

The Role of Grain Boundaries on Ionic Defect Migration in Metal Halide Perovskites

Phung

Al‐Ashouri

Meloni

et al. 2020

Advanced Energy Materials

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144

129

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“…This MD result is consistent with the YD prediction, θ YD = 0°. In fact, complete wetting is expected when Δ W > 0.17 N m −1 , and the adhesion energy of water on MAPI, Δ W ≈ 0.2 N m −1 is beyond this threshold . At the molecular level the origin of this large adhesion energy can be attributed to the strong PbO bond between water oxygen and lead atoms at the MAPI surface .…”

Section: Resultsmentioning

confidence: 99%

“…The YD equation gives the contact angle θ YD as a function of the solid–gas γ S , solid–liquid, γ SL , and liquid–gas, γ L , interface energies (see Figure , top) as

\cos θ_{YD} = \frac{γ_{normalS} - γ_{SL}}{γ_{normalL}}

The equation can be expressed also in terms of the liquid/solid wetting energy Δ W via the relation γ SL = γ L + γ S − Δ W as

θ_{YD} = \arccos (\frac{γ_{L} - normalΔ W}{γ_{L}})

Δ W and γ L in Equation can be obtained by atomistic simulations of planar surfaces and interfaces . Alternatively, the contact angle can be obtained by direct (finite temperature) simulations of a drop deposited on the surface, θ MD .…”

Section: Resultsmentioning

confidence: 99%

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Hydrophilicity and Water Contact Angle on Methylammonium Lead Iodide

Caddeo

Marongiu

Meloni

et al. 2018

Adv Materials Inter

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and by relating its value to the liquidsurface adhesion: the larger the adhesion, the smaller the contact angle. [1] Contact angle measurements have become accordingly a powerful yet cheap technique to quantify the water interaction with solid surfaces, a problem of huge technological importance in fluid dynamics, [2] aerospace engineering, [3] biology, [4] surface chemistry, [5] textile, [6] and materials science. [7] In photovoltaics, the interaction of water with surfaces is of great importance for example for organic and hybrid solar cells that are sensitive to humid conditions. This is the case of methylammonium lead iodide (CH 3 NH 3 PbI 3 or MAPI) which is at the core of the nowadays most efficient hybrid-based solar technology (with 23% maximum power conversion efficiencies [8][9][10][11] ) and which has potential applications also in the fields of optoelectronics, [12,13] lasing, [14][15][16][17][18] photocatalysis, [19] and thermoelectricity. [20][21][22] The interaction of MAPI with water is a major concern for such technology as it drives degradation in humid air and full decomposition in liquid water. [23][24][25] Accordingly, there is an increasing number of research items focusing on increasing the hydrophobicity of MAPI via, e.g., surface functionalization. In this context, contact angle measurements have been performed on pristine and hydrophobized films to assess their wettability. [26][27][28] Measurements of the contact angle of water on hybrid perovskites and, more in general, on soluble or transforming surfaces is challenging. If the substrate degrades, several nonequilibrium phenomena must be taken into account such as the solubilization and phase transformations of the solid. This led to ambiguous results on MAPI, with a contact angle that strongly depends on the time of measurement, [26][27][28] calling for a detailed microscopic investigation at the origin of the variability of the measured CA.Here, we combine molecular dynamics (MD) simulations with millisecond contact angle-measurements. We show that finite temperature MD simulations can reproduce experimental contact angles of water in a good agreement with the Young-Dupré (YD) continuum relation between liquid-solid adhesion and contact angle, and we explain the high CA value measured for water on MAPI as the result of the interaction of water with degraded superficial layers at the water/perovskite interface.Surface properties are often assessed with measurements of the contact angle of a water drop. The process is however flawed for the very important class of hybrid perovskite materials, extensively employed in solar cells and optoelectronics research, because they are water soluble and their surface degrades during contact angle measurements. While hybrid perovskites are considered to be highly hydrophilic, a contact angle with water of 83° can be measured, as if they were almost hydrophobic. By combining experiments and simulations, the actual value is explained as the result of the interaction of water with degraded superficial...

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“…[10][11][12] Several recent studies devoted to revealing the interaction mechanism between perovskites and water [13][14][15] have pointed out that weak interactions between the organic and inorganic constituents,p articularly at the surface of the perovskite,l ead to their rapid decomposition upon exposure to H 2 O. [16][17][18][19] To avoid this issue,b oth bulk perovskites and perovskite nanocrystals (PNCs) were synthesized in organic solvents,s uch as N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in the presence of hydrophobic organic ligands, [20][21][22][23][24] which help to provide basic protection from moisture. [25][26][27][28] Methods to further enhance their protection from aqueous environment include surface encapsulation with dense layers of polymers, [29][30][31] SiO 2 , [32,33] Al 2 O 3 , [34,35] and ZnO.…”

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Aqueous Synthesis of Methylammonium Lead Halide Perovskite Nanocrystals

Zhong

Rogach

et al. 2018

Angewandte Chemie

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Methylammonium lead halide perovskite nanocrystals offer attractive optoelectronic properties but suffer from fast degradation in the presence of water.I nc ontradiction to this observation, we demonstrate the possibility of ad irect aqueous synthesis of CH 3 NH 3 PbX 3 (X = Br or Cl/Br) nanocrystals through the reaction between the lead halide complex and methylamine when the pH is maintained in the range of 0-5. Under these synthetic conditions,t he positively charged surface of the perovskite nanocrystals and the proper ionic balance help to prevent their decomposition in water.A dditional surface capping with organic amine ligands further improves the photoluminescence quantum yield of the perovskite nanocrystals to values close to 40 %, ensures their stability under ambient conditions for several months,and their photoluminescence performance under continuous 0.1 Wmm À2 405 nm light irradiation for over 250 hours.Over the past several years,o rganic-inorganic methylammonium lead halide perovskites (CH 3 NH 3 PbX 3 ,X= Cl, Br, I) and all-inorganic cesium lead halide perovskites (CsPbX 3 , X = Cl, Br, I) have experienced unprecedented development both from the synthetic point of view and in terms of optical quality, [1][2][3][4][5] with potential for employment in optoelectronic devices. [6][7][8][9] However,t he moisture sensitivity of perovskites and their apparent instability upon contact with water remain as erious challenge which impedes their practical application. [10][11][12] Several recent studies devoted to revealing the interaction mechanism between perovskites and water [13][14][15] have pointed out that weak interactions between the organic and inorganic constituents,p articularly at the surface of the perovskite,l ead to their rapid decomposition upon exposure to H 2 O. [16][17][18][19] To avoid this issue,b oth bulk perovskites and perovskite nanocrystals (PNCs) were synthesized in organic solvents,s uch as N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in the presence of hydrophobic organic ligands, [20][21][22][23][24] which help to provide basic protection from moisture. [25][26][27][28] Methods to further enhance their protection from aqueous environment include surface encapsulation with dense layers of polymers, [29][30][31] SiO 2 , [32,33] Al 2 O 3 , [34,35] and ZnO. [36] Because of the anticipated general instability of perovskites in water, the aqueous synthesis route that is rather common for metal and classical semiconductor quantum dots [37][38][39] has never been considered as applicable for PNCs.A tt he same time,r ecent studies have pointed out the positive role of trace amounts of water in the formation of PNCs, [40] the self-healing of perovskite thin films, [41][42][43] and the possibility to perform the synthesis of perovskite/oxide Janus particles and phase transformation from organic solvents. [44] These observations imply the existence of as olubility equilibrium between perovskites and their saturated ionic components in water, which can eventually be shifted to...

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Collective Molecular Mechanisms in the CH₃NH₃PbI₃ Dissolution by Liquid Water

Cited by 84 publications

References 74 publications

The Role of Grain Boundaries on Ionic Defect Migration in Metal Halide Perovskites

The Role of Grain Boundaries on Ionic Defect Migration in Metal Halide Perovskites

Hydrophilicity and Water Contact Angle on Methylammonium Lead Iodide

Aqueous Synthesis of Methylammonium Lead Halide Perovskite Nanocrystals

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