Berlin 2018 – wissenschaftliches Programm
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 11: Dielectric, Elastic and Electromechanical Properties
KFM 11.4: Vortrag
Dienstag, 13. März 2018, 11:00–11:20, EMH 025
Dielectric Response - Answer to Many Questions in the Methylammonium Lead Halide Solar Cell Absorbers — •Doru C. Lupascu1, Irina Anusca1, Šarunas Svirskas2, Pascale Gemeiner3, Mehmet Sanlialp1, Gerhard Lackner1, Christian Fettkenhauer1, Jaroslavas Belovickis2, Vytautas Samulionis2, Maksim Ivanov2, Brahim Dkhil3, Juras Banys2, and Vladimir V. Shvartsman1 — 1Universität Duisburg-Essen, Essen, Deutschland — 2Vilnius University, Vilnius, Lithuania — 3Centralesupelec, Gif-sur-Yvette, France
Hybrid organic-inorganic perovskites CH3NH3PbX3 (X = I, Br, Cl) can potentially revolutionize the world of solar cells. The origin of the exceptionally large diffusion length of their photogenerated charge carriers, that is, their low recombination rate, remains elusive. We show that the dielectric constant conserves very high values (>27) for frequencies below 1 THz in all three halides. This efficiently prevents photocarrier trapping and their recombination owing to the strong screening. Similarly large contributions to the dielectric constant are attributed to the dipolar disorder of the CH3NH3+ cations as well as lattice dynamics in the Gigahertz range yielding dielectric constants of ε = 62 for the iodide, 58 for the bromide, and about 45 for the chloride below 1 GHz at room temperature. Disorder continuously reduces for decreasing temperature. Dipole dynamics prevail in the intermediate tetragonal phase. The low-temperature orthorhombic state is antipolar. No indications of ferroelectricity are found.