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Role of Methylammonium Rotation in Hybrid Halide MAPbX₃ (X = I, Br, and Cl) Perovskites by a Density Functional Theory Approach: Optical and Electronic Properties

Mehdizadeh, Ali, Akhtarianfar, Seyed Farshad, Shojaei, Saeid
Journal of physical chemistry 2019 v.123 no.11 pp. 6725-6734
absorption, anions, bromides, cations, chlorides, density functional theory, dielectric properties, geometry, iodides, optical properties, solar cells, spectral analysis
As a revolutionary material, hybrid halide perovskites can greatly improve the solar conversion efficiency of solar cells. In this work, a first-principles theoretical study is performed to investigate the role of methylammonium (MA) rotation in the MAPbX₃ (X = I, Br, and Cl) perovskites. To provide a full understanding of the MA rotation, we report electronic and optical properties in different rotational angles and modes. Our results evidence that rotation of MA with Rz and Rₓ modes causes substantial changes in band structure, density of states, partial density of states, electron density, dielectric function, and absorption spectra. We also showed that these changes are deeply affected by cation–cation (MA–Pb) and cation–anion (MA–X) interactions. Furthermore, the halogens of MAPbX₃ were changed to iodide, bromide, and chloride anions to study the inorganic–organic interactions inside the MAPbX₃ in detail. Interestingly, we conclude that the rotational modes, location, and orientation of organic cation can be used as an efficient tool to control the band gap, static dielectric constant, and absorption edge of the optical spectra. Our results providing useful and accurate insight into the behavior of MA embedded in inorganic octahedra are in good agreement with experimental data being used in photovoltaic applications.