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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 4: Perovskite and photovoltaics I (joint session HL/KFM)

KFM 4.11: Vortrag

Montag, 18. März 2024, 12:30–12:45, EW 203

Effective model for charge transport in hybrid organic-inorganic materials dominated by molecule-lattice interactions — •Florian Kluibenschedl, Georgios Koutentakis, Ragheed Alhyder, and Mikhail Lemeshko — Institute of Science and Technology Austria (ISTA), Am Campus 1, 3400 Klosterneuburg, Austria

The growing importance of crystalline hybrid materials with embedded molecular entities, such as hybrid organic-inorganic perovskites (HOIPs) or molecular organic frameworks, requires extensions of the conventional picture of charge transport based on electron-phonon interactions. Here we present a minimal, coarse-grained, two-dimensional model of charge transport based on the interactions of charge carriers with freely rotating molecules embedded in the inorganic lattice. Our phase diagram analysis reveals the presence of four phases, characterized by the distinct ordering of the molecular dipole moments, which strongly depends on the tunneling anisotropy of the carriers as well as on the strength of carrier-molecule interactions. The most striking outcome is the coexistence of degenerate ferroelectric phases of reduced symmetry beyond a certain threshold of interaction strength, even in the case of isotropic tunneling. The coexistence of these phases motivates a symmetry breaking mechanism similar to the Jahn-Teller effect, which introduces transport anisotropy into an otherwise symmetric system. We relate these results to the proposed formation of ferroelectric large polarons as an explanation of the remarkable optoelectronic properties of HOIPs.

Keywords: Ferroelectric Polarons; Hybrid Organic-Inorganic Perovskites; Molecule-Lattice Interactions; Anisotropic Charge Transport; Symmetry Breaking