Atomistic Simulations of Methylammonium Lead Halide Layers on PbTiO3 (001) Surfaces

Plugaru, Neculai; Nemnes, George Alexandru; Filip, Lucian; Pintilie, Ioana; Pintilie, Lucian; Butler, Keith Tobias; Manolescu, Andrei

Atomistic Simulations of Methylammonium Lead Halide Layers on PbTiO3 (001) Surfaces

2017

The substantial increase in the power conversion efficiency of hybrid perovskite solar cells, to date reaching more than 20% in the laboratory, has strongly motivated research on this class of organic–inorganic materials and related devices, particularly based on CH₃NH₃PbI₃–ₓXₓ/TiO₂ heterostructures (X = Cl,Br). Taking under consideration that a ferroelectric substrate may act as an efficient electron transporter, positively influencing charge collection across the interface and allowing the tuning of the halide perovskite (HP) - ferroelectric junction, we performed extensive density functional theory calculations on CH₃NH₃PbI₃–ₓClₓ layers deposited on tetragonal PbTiO₃ (PTO) (001) surfaces, to study their structural and electronic properties. The main findings of this study are as follows. (i) A ferroelectric polarization pointing from the PTO/HP interface to the PTO is favorable for the photogenerated electrons transfer across the interface and their transport to the collecting electrode. (ii) The PTO internal electric field leads to a position dependent energy levels diagram. (iii) The HP gap may be tuned by chlorine concentration at the interface, as well as the by the surface terminations of PbTiO₃ and hybrid perovskite layers. (iv) The presence of the PTO ferroelectric surface is likely to have just a slight orientational effect on the (CH₃NH₃)⁺ dipoles.

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