Center for Molecular Modeling - M. Roeffaers

Additivity of atomic strain fields as a tool to strain-engineering phase-stabilized CsPbI3 perovskites

leen — Mon, 13 Nov 2023 10:15:01 +0000

J. Teunissen, T. Braeckevelt, I. Skvortsova, J. Guo, B. Pradhan, E. Debroye, M. Roeffaers, J. Hofkens, S. Van Aert, S. Bals, S.M.J. Rogge, V. Van Speybroeck

The Journal of Physical Chemistry C

127, 48, 23400-23411

2023

Abstract

CsPbI₃ is a promising perovskite material for photovoltaic applications in its photoactive perovskite or black phase. However, the material degrades to a photovoltaically inactive or yellow phase at room temperature. Various mitigation strategies are currently being developed to increase the lifetime of the black phase, many of which rely on inducing strains in the material that hinder the black-to-yellow phase transition. Physical insight into how these strategies exactly induce strain as well as knowledge of the spatial extent over which these strains impact the material is crucial to optimize these approaches but is still lacking. Herein, we combine machine learning potential-based molecular dynamics simulations with our in silico strain engineering approach to accurately quantify strained large-scale atomic structures on a nanosecond time scale. To this end, we first model the strain fields introduced by atomic substitutions as they form the most elementary strain sources. We demonstrate that the magnitude of the induced strain fields decays exponentially with the distance from the strain source, following a decay rate that is largely independent of the specific substitution. Second, we show that the total strain field induced by multiple strain sources can be predicted to an excellent approximation by summing the strain fields of each individual source. Finally, through a case study, we illustrate how this additive character allows us to explain how complex strain fields, induced by spatially extended strain sources, can be predicted by adequately combining the strain fields caused by local strain sources. Hence, the strain additivity proposed here can be adopted to further our insight into the complex strain behavior in perovskites and to design strain from the atomic level onward to enhance their sought-after phase stability.

Open Access version available at UGent repository

Gold Open Access

DOI

http://dx.doi.org/10.1021/acs.jpcc.3c05770

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teunissen-et-al-2023-additivity-of-atomic-strain-fields-as-a-tool-to-strain-engineering-phase-stabilized-cspbi3.pdf

Accurately Determining the Phase Transition Temperature of CsPbI3 via Random-Phase Approximation Calculations and Phase-Transferable Machine Learning Potentials

tbraeckevelt — Sat, 11 Jun 2022 18:44:03 +0000

T. Braeckevelt, R. Goeminne, S. Vandenhaute, S. Borgmans, T. Verstraelen, J.A. Steele, M. Roeffaers, J. Hofkens, S.M.J. Rogge, V. Van Speybroeck

Chemistry of Materials

34, 19, 8561–8576

2022

Abstract

While metal halide perovskites (MHPs) have shown great potential for various optoelectronic applications, their widespread adoption in commercial photovoltaic cells or photosensors is currently restricted, given that MHPs such as CsPbI₃ and FAPbI₃ spontaneously transition to an optically inactive nonperovskite phase at ambient conditions. Herein, we put forward an accurate first-principles procedure to obtain fundamental insight into this phase stability conundrum. To this end, we computationally predict the Helmholtz free energy, composed of the electronic ground state energy and thermal corrections, as this is the fundamental quantity describing the phase stability in polymorphic materials. By adopting the random phase approximation method as a wave function-based method that intrinsically accounts for many-body electron correlation effects as a benchmark for the ground state energy, we validate the performance of different exchange-correlation functionals and dispersion methods. The thermal corrections, accessed through the vibrational density of states, are accessed through molecular dynamics simulations, using a phase-transferable machine learning potential to accurately account for the MHPs’ anharmonicity and mitigate size effects. The here proposed procedure is critically validated on CsPbI₃, which is a challenging material as its phase stability changes slowly with varying temperature. We demonstrate that our procedure is essential to reproduce the experimental transition temperature, as choosing an inadequate functional can easily miss the transition temperature by more than 100 K. These results demonstrate that the here validated methodology is ideally suited to understand how factors such as strain engineering, surface functionalization, or compositional engineering could help to phase-stabilize MHPs for targeted applications.

Open Access version available at UGent repository

Gold Open Access

DOI

https://doi.org/10.1021/acs.chemmater.2c01508

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acs.chemmater.2c01508.pdf

Texture Formation in Polycrystalline Thin Films of All-Inorganic Lead Halide Perovskite

sven — Sat, 16 Jan 2021 12:42:12 +0000

J.A. Steele, E. Solano, H. Jin, V. Prakasam, T. Braeckevelt, H. Yuan, Z. Lin, R. de Kloe, Q. Wang, S.M.J. Rogge, V. Van Speybroeck, D. Chernyshov, J. Hofkens, M. Roeffaers

Advanced Materials

33 (13), 2007224

2021

Abstract

Controlling grain orientations within polycrystalline all-inorganic halide perovskite solar cells can help increase conversion efficiencies toward their thermodynamic limits, however the forces governing texture formation are ambiguous. Using synchrotron X-ray diffraction, we report meso-structure formation within polycrystalline CsPbI_2.85Br_0.15 powders as they cool from a high-temperature cubic perovskite (α-phase). Tetragonal distortions (β-phase) trigger preferential crystallographic alignment within polycrystalline ensembles, a feature we suggest is coordinated across multiple neighboring grains via interfacial forces that select for certain lattice distortions over others. External anisotropy is then imposed on polycrystalline thin films of orthorhombic (γ-phase) CsPbI_3-xBr_x perovskite via substrate clamping, revealing two fundamental uniaxial texture formations; (i) I-rich films possess orthorhombic-like texture (<100> out-of-plane; <010> and <001> in-plane), while (ii) Br-rich films form tetragonal-like texture (<110> out-of-plane; <1-10> and <001> in-plane). In contrast to relatively uninfluential factors like the choice of substrate, film thickness and annealing temperature, Br incorporation modifies the γ-CsPbI_3-xBr_x crystal structure by reducing the orthorhombic lattice distortion (making it more tetragonal-like) and governs the formation of the different, energetically favored textures within polycrystalline thin films.

DOI

http://dx.doi.org/10.1002/adma.202007224

Thermal unequilibrium of strained black CsPbI3 thin films

sven — Thu, 25 Jul 2019 18:07:18 +0000

J.A. Steele, H. Jin, I. Dovgaliuk, R.F. Berger, T. Braeckevelt, H. Yuan, C. Martin, E. Solano, K. Lejaeghere, S.M.J. Rogge, C. Notebaert, W. Vandezande, K.P.F. Janssen, B. Goderis, E. Debroye, Y.-K. Wang, Y. Dong, D. Ma, M. Saidaminov, H. Tan, Z. Lu, V. Dyadkin, D. Chernyshov, V. Van Speybroeck, E.H. Sargent, J. Hofkens, M. Roeffaers

Science

365 (6454), 679-684

2019

Abstract

The high-temperature all-inorganic CsPbI₃ perovskite black phase is metastable relative to its yellow non-perovskite phase, at room temperature. Since only the black phase is optically active, this represents an impediment for the use of CsPbI₃ in optoelectronic devices. We report the use of substrate clamping and biaxial strain to render stable, at room temperature, black phase CsPbI₃ thin films. We used synchrotron-based grazing incidence wide angle x-ray scattering to track the introduction of crystal distortions and strain-driven texture formation within black CsPbI₃ thin films when they were cooled following annealing at 330°C. The thermal stability of black CsPbI₃ thin films is vastly improved by the strained interface, a response verified by ab initio thermodynamic modelling.

Open Access version available at UGent repository

Gold Open Access

DOI

http://dx.doi.org/10.1126/science.aax3878

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science.aax3878.full_.pdf

Active Role of Methanol in Post-Synthetic Linker Exchange in the Metal-Organic Framework UiO-66

wim — Wed, 14 Nov 2018 08:06:51 +0000

J. Marreiros, C. Caratelli, J. Hajek, A. Krajnc, G. Fleury, B. Bueken, D. De Vos, G. Mali, M. Roeffaers, V. Van Speybroeck, R. Ameloot

Chemistry of Materials

31 (4), 1359-1369

2019

Abstract

UiO-66 is known as one of the most robust metal-organic framework materials. Nevertheless, UiO-66 has also been shown to undergo post-synthetic exchange of structural linkers with surprising ease in some sol-vents. To date the exchange mechanism has not yet been fully elucidated. Here, we show how time-resolved monitoring grants insight into the selected case of exchanging 2-aminoterephthalic acid into UiO-66 in methanol. Analysis of both the solid and liquid phase, complemented by computational insights, revealed the active role of methanol in the creation and stabilization of metastable states in which dangling linkers are similar to monocarboxylate defects that can be introduced during UiO-66 synthesis, such dangling link-ers undergo fast exchange. The presence of missing linker or missing cluster defects at the start of the ex-change process was shown to have no considerable impact on the equilibrium composition. After the ex-change process, the incoming 2-aminoterephthalate and remaining terephthalate linkers were distributed homogeneously in the framework for the typical small crystal size of UiO-66 (≈500nm).

Open Access version available at UGent repository

Green Open Access

DOI

http://dx.doi.org/10.1021/acs.chemmater.8b04734

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Accurately determining the transition temperature of metal halide perovskites via RPA calculations and phase-transferable machine learning potentials

tbraeckevelt — Thu, 07 Jul 2022 11:37:18 +0000

T. Braeckevelt, R. Goeminne, S. Vandenhaute, S. Borgmans, T. Verstraelen, J.A. Steele, M. Roeffaers, J. Hofkens, S.M.J. Rogge, V. Van Speybroeck

ISBN/ISSN:

Talk

Conference / event / venue

DFT2022

Brussels, Belgium

Monday, 29 August, 2022 to Friday, 2 September, 2022

Abstract (private)

Braeckevelt_abstract.pdf

Stabilizing the perovskite phase of cesium lead iodide thin films via interfacial strains

tbraeckevelt — Sun, 19 Jan 2020 14:46:54 +0000

T. Braeckevelt, J.A. Steele, K. Lejaeghere, S.M.J. Rogge, M. Roeffaers, J. Hofkens, V. Van Speybroeck

ISBN/ISSN:

Poster

Conference / event / venue

MolSim-2020: Understanding Molecular Simulation

Amsterdam, The Netherlands

Monday, 6 January, 2020 to Friday, 17 January, 2020

Stabilizing the perovskite phase of cesium lead iodide thin films via interfacial strains

tbraeckevelt — Sun, 19 Jan 2020 14:43:28 +0000

T. Braeckevelt, J.A. Steele, K. Lejaeghere, S.M.J. Rogge, M. Roeffaers, J. Hofkens, V. Van Speybroeck

ISBN/ISSN:

Poster

Conference / event / venue

5th International Conference on Perovskite Solar Cells and Optoelectronics (PSCO19)

Lausanne, Switzerland

Monday, 30 September, 2019 to Wednesday, 2 October, 2019

Stabilizing the perovskite phase of cesium lead iodide thin films via interfacial strains

tbraeckevelt — Sun, 19 Jan 2020 14:38:11 +0000

T. Braeckevelt, J.A. Steele, K. Lejaeghere, S.M.J. Rogge, M. Roeffaers, J. Hofkens, V. Van Speybroeck

ISBN/ISSN:

Poster

Conference / event / venue

ICAMM conference

Rennes, France

Monday, 1 July, 2019 to Wednesday, 3 July, 2019

Enhanced base catalytic activity of M2(BTC)(NO3)(DMF) via controlled structure modification

mat — Wed, 05 Nov 2014 10:11:33 +0000

D. Jonckheere, P. Valvekens, T. De Baerdemaeker, A. Kubarev, M. Vandichel, K. Hemelsoet, M. Waroquier, V. Van Speybroeck, M. Roeffaers, D. De Vos

P19

ISBN/ISSN:

Poster

Conference / event / venue

DZA2014

Ghent, Belgium

Tuesday, 7 October, 2014