Regensburg 2016 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 54: Hybrid and Perovskite Photovoltaics IV (joint session CPP/DF/DS/HL, organized by HL)

CPP 54.2: Vortrag

Donnerstag, 10. März 2016, 15:00–15:15, H2

Structural properties of hybrid perovskites from first principles — •Jingrui Li¹, Jari Järvi^1,2, Hugo Levard¹, and Patrick Rinke¹ — ¹Aalto University, Helsinki, Finland — ²University of Helsinki, Finland

Hybrid perovskites have received rapidly growing interest in recent years as promising photoactive materials in emergent photovoltaic technologies. We present a first-principles analysis of the atomistic structure of the methylammonium lead triiodide (CH₃NH₃PbI₃) perovskite in this work, with a particular focus on the orientation of CH₃NH₃⁺ cations and its interplay with the inorganic matrix. Relativistic density functional theory calculations were performed using the all-electron local-atomic-orbital code FHI-aims. Our results indicate that (i) the lattice constants obtained by incorporating the long-range van der Waals interactions (using the Tkatchenko-Scheffler method) in the PBE exchange-correlation functional agree well with experiments; (ii) hydrogen bonding between the ammonium group and the I⁻ anions plays the decisive role in the position of the CH₃NH₃⁺ cation and the shape of the PbI₃²⁻ framework; (iii) the reorientation of CH₃NH₃⁺ is limited due to the high barriers (∼ 80 meV). Based on these findings we establish a self-consistent multiscale model, in which the energetically favorable alignment of CH₃NH₃⁺ dipoles in the material is determined by combining classical electrostatics and statistics with structure relaxation in DFT. Our procedure produces representative “pseudo random” methylammonium lead triiodide supercells that will form the basis of further first-principles work.