Dynamical properties of hybrid perovskites by large scale model potential molecular dynamics

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Oral, Alessandro Mattoni, presentation 246
Publication date: 5th February 2015

The success of hybrid lead halide perovskites in photovoltaics has given rise to an intense research effort to study its fundamental properties and the role of the organic and inorganic components in the hybrid material. For what concerns the electronic properties, it has been shown that the electronic levels of the molecules are not directly involved. In particular, intrinsic recombination and photovoltaic properties can be calculated by describing the material as an inorganic semiconductor with a hybrid body [1]. However, the actual molecular orientations have an impact on the distortions of the inorganic lattice and, to some extent, on the transport properties [2]. At finite temperature, the interplay between the rotational dynamics of the molecules and the inorganic lattice is important to understand the relaxation processes within the material. A number of theoretical studies have been performed recently by means of first-principles calculations ( e.g. [3]). However, the computational cost of such methods limits the size of the systems that are computationally affordable.  A comprehensive study of the effect of temperature on the molecular ordering and the corresponding correlation functions  requires new methods able to extend the time and length scale of atomistic models. Here, we report a novel model potential for the study of the structural and dynamical properties of the material at a reduced computational cost [3]. By performing molecular dynamics simulations of large scale atomistic models of methylammonium lead halide in the nanosecond scale, we are able to calculate the reorientational times of the molecules and the dynamical properties under controlled thermodynamical conditions  spanning from the orthorhombic to the cubic phase of the perovskite. The results are consistent with the available experimental data and first-principles calculations and make possible to clarify the temperature dependence of the dynamical processes. Present model potential opens the way to the large scale finite temperature simulations of hybrid perovskites and its nanostructures.

[1] Filippetti, A.; Delugas, P.; Mattoni, A. Methylammonium Lead-Iodide Perovskite: Recombination and Photoconversion of an Inorganic Semiconductor Within a Hybrid Body. J. Phys. Chem. C 2014, 118, 24843 [2]Filippetti, A.; Mattoni, A. Hybrid Perovskites for Photovoltaics: Insights from First Principles. Phys. Rev. B 2014, 89, 125203. [3]Quarti, C.; Mosconi, E.; De Angelis, F. Interplay of Orientational Order and Electronic Structure in Methylammonium Lead Iodide: Implications for Solar Cells Operation. Chem. Mater. 2014, 26, 6557-6569. [4]Mattoni A.; Delugas P;Filippetti A; "Methylammonium reorientational dynamics in hybrid perovskites by model potential molecular dynamics"submitted for publication

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