Efficient modelling of ion structure and dynamics in inorganic metal halide perovskites

Salvador R.G. Balestra, Jose Manuel Vicent-Luna, Sofia Calero, Shuxia Tao (Corresponding author), Juan A. Anta (Corresponding author)

Research output: Contribution to journalArticleAcademicpeer-review

27 Citations (Scopus)

Abstract

Metal halide perovskites (MHPs) are nowadays one of the most studied semiconductors due to their exceptional performance as active layers in solar cells. Although MHPs are excellent solid-state semiconductors, they are also ionic compounds, where ion migration plays a decisive role in their formation, their photovoltaic performance and their long-term stability. Given the above-mentioned complexity, molecular dynamics simulations based on classical force fields are especially suited to study MHP properties, such as lattice dynamics and ion migration. In particular, the possibility to model mixed compositions is important since they are the most relevant to optimize the optical band gap and the stability. With this intention, we employ DFT calculations and a genetic algorithm to develop a fully transferable classical force field valid for the benchmark inorganic perovskite compositional set CsPb(BrxI1-x)3 (x = 0, 1/3, 2/3, 1). The resulting force field reproduces correctly, with a common set of parameters valid for all compositions, the experimental lattice parameter as a function of bromide/iodide ratio, the ion-ion distances and the XRD spectra of the pure and mixed structures. The simulated elastic constants, thermal conductivities and ion migration activation energies of the pure compounds are also in good agreement with experimental trends. Our molecular dynamics simulations make it possible to predict the compositional dependence of the ionic diffusion coefficient on bromide/iodide ratio and vacancy concentration. Interestingly, compared to the pure compounds, we found a significantly lower activation energy for vacancy migration and faster diffusion for the mixed perovskites. This anomalous effect helps to understand the photoinduced phase segregation observed in the mixed perovskite. The method presented here represents a first step towards the generation of fully generic classical force fields of pure and mixed photovoltaic perovskites using genetic algorithms that optimize the required parameters for a wide range of lattice deformations.

Original languageEnglish
Pages (from-to)11824-11836
Number of pages13
JournalJournal of Materials Chemistry A
Volume8
Issue number23
DOIs
Publication statusPublished - 21 Jun 2020

Funding

We thank Ministerio de Ciencia e Innovación of Spain, Agencia Estatal de Investigación (AEI) and EU (FEDER) under grants MAT2016-79866-R and PCI2019-111839-2 (SOLAR COFUND 2, project SCALEUP) for nancial support. We thank Junta de Andalućıa for support under grant SOLARFORCE (UPO-1259175). S.T. acknowledges funding by the Computational Sciences for Energy Research (CSER) tenure track program of Shell and NWO (Project number 15CST04-2), the Netherlands. S. R. G. B. thanks Spanish Ministerio de Economía, Industria y Competitividad for his predoctoral and postdoctoral fellowship (BES-2014-067825 from CTQ2013-48396 P). We also thank C3UPO for the HPC support.

FundersFunder number
Junta de AndalućıaUPO-1259175
Ministerio de Ciencia e Innovación
Shell
European Commission
Nederlandse Organisatie voor Wetenschappelijk Onderzoek15CST04-2
European Regional Development FundPCI2019-111839-2, MAT2016-79866-R
Ministerio de Economía y Competitividad del Gobierno de EspañaBES-2014-067825
Agencia Estatal de Investigación

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