Properties of Hybrid Organic-Inorganic Perovskites

Hybrid organic-inorganic perovskites (HOIPs) have emerged as promising semiconducting materials for photovoltaics and light emitting devices. We are interested in probing the fundamental timescales of thermal dissipation processes in these hybrid materials comprised of organic and inorganic sublattices using transient absorption spectroscopy. As shown below, using the absorption coefficient of organic phonon modes as an indicator of lattice temperature, we observed an unusually slow thermal equilibration between the organic and inorganic sublattices.

Two-dimensional HOIPs are formed by inserting organic cationic layers into the perovskite layers in 3D HOIPs. In such hierarchical architectures, strong quantum and dielectric confinement effects, produced by the organic spacer layers, result in large exciton binding energy and strong excitonic character of photo-generated electron-hole pairs. We investigated fundamental optical properties of 2D HOIPs, such as their complex dielectric functions, using a newly developed dielectric-coating based technique.

In addition to strong excitonic effects, the layered, organic-inorganic arrangement in 2D HOIPs lend themselves to extremely large acoustic impedance mismatch, that may influence acoustic phonon characteristics. Using transient reflection technique, we studied propagation of acoustic phonons in these “superlattice” structures with systematically varied perovskite thickness. We use simple toy models to corroborate our experimental results.

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