Research

Overview

We are interested in condensed-phase, organic and inorganic semiconducting materials that unlike standard semiconductors (e.g. Silicon and Gallium Arsenide), exhibit strong anharmonic nuclear motion at room temperature. Such solids are typically softer than standard semiconductors as they are held by weak London forces or loose ionic bonds rather than covalent bonds. Therefore, the static band-structure picture, that successfully describes the electronic properties of standard semiconductors, cannot fully explain the electronic properties of these materials.

Methods

We combine optical spectroscopy and charge transport measurements at various conditions and temperatures. Spectroscopic techniques include low-frequency (Terahertz range) Raman scattering, reflectance and photoluminescence. Our setups are assembled in-house and are modified according to the specific requirements of each experiment.

Hybrid perovskites

Hybrid perovskites are comprised of an organic molecule and an inorganic metal-halide network that are bound together through loose ionic bonds. They exhibit rich chemical, structural, and optical tunability that is strongly affected by the properties of the organic molecule. The tunability and flexibility of these hybrid perovskites makes them an ideal testbed for the investigation of the coupling between structural and electronic dynamics in “soft” semiconductors.

Organic single crystals

Organic crystals are structurally well-defined and thus present ideal conditions to test theoretical models of electronic structure and transport, including the relation between structure and function. Unlike inorganic semiconductors, molecular semiconductors are “soft", as they are primarily bound by weak van der Waals interactions. Thus, at room temperature, they exhibit low-frequency intermolecular nuclear motion in addition to high-frequency intramolecular vibrations. We study how a charge carrier moving through the material and experiences the complex interplay with a dynamical and responsive potential.

Semi-conducting polymers

Conjugated, semiconducting polymers have a substantial technological appeal in the field of printed electronics and organic photovoltaic cells (OPVs). Unlike molecular crystals and hybrid perovskites, conjugated polymers are macromolecules with numerous degrees of conformational freedom, resulting in microstructures varying from amorphous to semi-crystalline. The interplay between microstructure and electrical properties in conjugated polymers is not well understood. Specifically, we strive to understand how low frequency motions differ between the amorphous and ordered regions of polymer films and how they affect charge transport properties.

Non-classical crystallization pathways of carbonate based minerals

Unlike classical mechanism of monomer-by-monomer growth, non-classical crystallization processes involve mesoscopic-particle attachment and oriented attachment. Evidence for the abundance and significance of these pathways is rapidly increasing in the literature. A major driving force for these investigations originates from biomineralization where carbonate based minerals play a central role.  We study solidification pathways of carbonate-based mineral by probing, in real-time, “external” vibrational  modes which are due to collective motion of entire unit cells of large molecular complexes.