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Regensburg 2016 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 80: Hybrid and Perovskite Photovoltaics IV (Joint session of CPP, DF, DS and HL, organized by HL)

HL 80.2: Talk

Thursday, March 10, 2016, 15:00–15:15, H2

Structural properties of hybrid perovskites from first principles — •Jingrui Li1, Jari Järvi1,2, Hugo Levard1, and Patrick Rinke11Aalto 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.

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