Pressure-induced effects in the inorganic halide perovskite CsGeI<sub>3</sub>

Liu, Diwen; Li, Qiaohong; Jing, Huijuan; Wu, Kechen

doi:10.1039/c8ra10251a

Cited by 86 publications

(43 citation statements)

References 48 publications

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“…The strain‐dependent structural changes were compared with the reported results for halide materials with the selected examples of M  X bond lengths as seen in Figure 4d. [ 36,43–47 ] The clear dependence of the bond length on the applied strain is very apparent by demonstrating the reduced bond lengths with the compressive strain. The reported differences in the bond length are based on the theoretical simulations incorporating the higher compressive or tensile strain values up to ≈10%.…”

Section: Resultsmentioning

confidence: 99%

Anisotropic In Situ Strain‐Engineered Halide Perovskites for High Mechanical Flexibility

Kim

Lee

Cho

2020

Adv Funct Materials

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Even though halide perovskite materials have been increasingly investigated as flexible devices, mechanical properties under flexible environments have rarely been reported on. Herein, a nonconventional deposition technique that can generate extra compressive or tensile stress in representative inorganic CsPbBr3 and hybrid MAPbI3 (methylammonium lead iodide) halide perovskites is proposed for higher mechanical flexibility. As an impressive result of bending fracture evaluation, fracture energy is substantially improved by ≈260% for CsPbBr3 and ≈161% for MAPbI3 with the maximum compressive strain of −1.33%. Origin of the flexibility enhancements by the in situ strain is verified with structural simulation where the anisotropic lattice distortion, that is, contraction in the ab plane and elongation along the c‐axis, is evident with changes in atomic bond lengths and angles in the halide perovskites. Other mechanical properties such as hardness, film strength, and fracture toughness are also discussed with direct comparisons between the inorganic and hybrid halides. Beyond the successful adjustment of this in situ deposition technique, the strain‐dependent mechanical properties are expected to be extensively useful for designing halides‐based flexible devices.

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Section: Resultsmentioning

confidence: 99%

Anisotropic In Situ Strain‐Engineered Halide Perovskites for High Mechanical Flexibility

Kim

Lee

Cho

2020

Adv Funct Materials

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“…From the literature it is evident that most of the halide perovskites follow similar band structure [27,28] and thus the descriptor model universalize the Eg variation under different types of strain. Also, in the context of uniform expansion or compression it has been shown that irrespective of the exchange-correlation (XC) functional, the variation of the bandgap with compression and expansion remains the same [13,[34][35][36]. The same is expected for the case of epitaxial strain.…”

Section: B Construction Of a Descriptor Modelmentioning

confidence: 88%

Defining the topological influencers and predictive principles to engineer the band structure of halide perovskites

2020

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Complex quantum coupling phenomena of halide perovskites are examined through ab-initio calculations and exact diagonalization of model Hamiltonians to formulate a set of fundamental guiding rules to engineer the bandgap through strain. The bandgap tuning in halides is crucial for photovoltaic applications and for establishing non-trivial electronic states. Using CsSnI3 as the prototype material, we show that in the cubic phase, the bandgap reduces irrespective of the nature of strain. However, for the tetragonal phase, it reduces with tensile strain and increases with compressive strain, while the reverse is the case for the orthorhombic phase. The reduction can give rise to negative bandgap in the cubic and tetragonal phases leading to normal to topological insulator phase transition. Also, these halides tend to form a stability plateau in a space spanned by strain and octahedral rotation. In this plateau, with negligible cost to the total energy, the bandgap can be varied in a range of 1eV. Furthermore, we present a descriptor model for the perovskite to simulate their bandgap with strain and rotation. Analysis of band topology through model Hamiltonians led to the conceptualization of topological influencers that provide a quantitative measure of the contribution of each chemical bonding towards establishing a normal or topological insulator phase. On the technical aspect, we show that a four orbital based basis set (Sn-{s,p} for CsSnI3) is sufficient to construct the model Hamiltonian which can explain the electronic structure of each polymorph of halide perovskites.

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“…However, there are few studies on the photoelectric properties of CsGeI 3 under pressure. Although Liu et al studied some photoelectric properties of CsGeI 3 under hydrostatic pressure through first-principles, we still do not know enough about it [25]. Based on the first-principles, the change of photoelectric property of CsGeI 3 was explored at the hydrostatic pressure from −0.5 GPa to 0.5 GPa.…”

Section: Introductionmentioning

confidence: 99%

First-Principles Study on the Photoelectric Properties of CsGeI3 under Hydrostatic Pressure

2020

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CsGeI3 has been widely studied as an important photoelectric material. Based on the density functional theory (DFT), we use first-principles to study the photoelectric properties of CsGeI3 by applying successive hydrostatic pressure. It has been found that CsGeI3 has an optimal optical band gap value of 1.37 eV when the applied pressure is −0.5 GPa, so this paper focuses on the comparative study of the photoelectric properties when the pressure is −0.5 GPa and 0 GPa. The results showed that CsGeI3 has a higher dielectric value, conductivity, and absorption coefficient and blue shift in absorption spectrum when the pressure is −0.5 GPa. By calculating and comparing the effective masses of electrons and holes and the exciton binding energy, it was found that their values are relatively small, which indicates that CsGeI3 is an efficient light absorbing material. CsGeI3 was found to be stable under both pressure conditions through multiple calculations of the Born Huang stability criterion, tolerance factor T, and phonon spectrum with or without virtual frequency. We also calculated the elastic modulus of both pressure conditions and found that they are both soft, ductile, and anisotropic. Finally, the thermal properties of CsGeI3 under two kinds of pressure were studied. It was found that the Debye temperature and heat capacity of CsGeI3 increased with the increase of thermodynamic temperature, and the Debye temperature increased rapidly after pressure, while the heat capacity slowly increased and finally stabilized. Through the calculation of enthalpy, entropy, and Gibbs free energy of CsGeI3, it was found that the Gibbs free energy decreases faster with the increase of temperature without applied pressure, which indicates that CsGeI3 has a higher stability without pressure. Through the comparative analysis of the photoelectric properties of CsGeI3 under pressure, it was found that CsGeI3 after applied pressure is a good photoelectric material and suitable for perovskite solar cells (PSCs) material.

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Pressure-induced effects in the inorganic halide perovskite CsGeI₃

Abstract: Perovskite photovoltaic materials are gaining significant attention due to their excellent photovoltaic properties.

Cited by 86 publications

References 48 publications

Anisotropic In Situ Strain‐Engineered Halide Perovskites for High Mechanical Flexibility

Anisotropic In Situ Strain‐Engineered Halide Perovskites for High Mechanical Flexibility

Defining the topological influencers and predictive principles to engineer the band structure of halide perovskites

First-Principles Study on the Photoelectric Properties of CsGeI3 under Hydrostatic Pressure

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Pressure-induced effects in the inorganic halide perovskite CsGeI3

Abstract: Perovskite photovoltaic materials are gaining significant attention due to their excellent photovoltaic properties.

Cited by 86 publications

References 48 publications

Anisotropic In Situ Strain‐Engineered Halide Perovskites for High Mechanical Flexibility

Anisotropic In Situ Strain‐Engineered Halide Perovskites for High Mechanical Flexibility

Defining the topological influencers and predictive principles to engineer the band structure of halide perovskites

First-Principles Study on the Photoelectric Properties of CsGeI3 under Hydrostatic Pressure

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Pressure-induced effects in the inorganic halide perovskite CsGeI₃