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Two-dimensional (2D) hybrid perovskites are stoichiometric compounds consisting of alternating inorganic metal-halide sheets and organoammonium cationic layers. This materials class is widely tailorable in composition, structure, and dimensionality and is providing an intriguing playground for the solid-state chemistry and physics communities to uncover structure-property relationships. In this Perspective, we describe semiconducting 2D perovskites containing lead and tin halide inorganic frameworks. In these 2D perovskites, charges are typically confined to the inorganic framework because of strong quantum and dielectric confinement effects, and exciton binding energies are many times greater than kT at room temperature. We describe the role of the heavy atoms in the inorganic framework; the geometry and chemistry of organic cations; and the "softness" of the organic-inorganic lattice on the electronic structure and dynamics of electrons, excitons, and phonons that govern the physical properties of these materials.

Passivating surface defects and controlling the carrier concentration and mobility in quantum dot (QD) thin films is prerequisite to designing electronic and optoelectronic devices. We investigate the effect of introducing indium in CdSe QD thin films on the dark mobility and the photogenerated carrier mobility and lifetime using field-effect transistor (FET) and time-resolved microwave conductivity (TRMC) measurements. We evaporate indium films ranging from 1 to 11 nm in thickness on top of approximately 40 nm thick thiocyanate-capped CdSe QD thin films and anneal the QD films at 300 °C to densify and drive diffusion of indium through the films. As the amount of indium increases, the FET and TRMC mobilities and the TRMC lifetime increase. The increase in mobility and lifetime is consistent with increased indium passivating midgap and band-tail trap states and doping the films, shifting the Fermi energy closer to and into the conduction band.