Phase Transitions of Formamidinium Lead Iodide Perovskite under Pressure.

The pressure-induced structural evolution of formamidinium-based perovskite FAPbI was investigated using in situ synchrotron X-ray diffraction and laser-excited photoluminescence methods. Cubic α-FAPbI ( Pm3̅ m) partially and irreversibly transformed to hexagonal δ-FAPbI ( P6 mc) at a pressure less than 0.1 GPa.

Publisher Correction: Selective enhancement of optical nonlinearity in two-dimensional organic-inorganic lead iodide perovskites.

In the PDF version of this article, Eq. 5 is missing all elements after the equals sign. The correct version of Eq.

Selective enhancement of optical nonlinearity in two-dimensional organic-inorganic lead iodide perovskites.

Reducing the dimensionality of three-dimensional hybrid metal halide perovskites can improve their optoelectronic properties. Here, we show that the third-order optical nonlinearity, n , of hybrid lead iodide perovskites is enhanced in the two-dimensional Ruddlesden-Popper series, (CH(CH)NH)(CHNH) Pb I (n = 1-4), where the layer number (n) is engineered for bandgap tuning from E  = 1.60 eV (n = ∞; bulk) to 2.

Multiphoton Absorption Order of CsPbBr As Determined by Wavelength-Dependent Nonlinear Optical Spectroscopy.

CsPbBr is a direct-gap semiconductor where optical absorption takes place across the fundamental bandgap, but this all-inorganic halide perovskite typically exhibits above-bandgap emission when excited over an energy level, lying above the conduction-band minimum. We probe this bandgap anomaly using wavelength-dependent multiphoton absorption spectroscopy and find that the fundamental gap is strictly two-photon forbidden, rendering it three-photon absorption (3PA) active. Instead, two-photon absorption (2PA) commences when the two-photon energy is resonant with the optical gap, associated with the level causing the anomaly.

Low-Temperature Cationic Rearrangement in a Bulk Metal Oxide.

Cationic rearrangement is a compelling strategy for producing desirable physical properties by atomic-scale manipulation. However, activating ionic diffusion typically requires high temperature, and in some cases also high pressure in bulk oxide materials. Herein, we present the cationic rearrangement in bulk Mn2 FeMoO6 at unparalleled low temperatures of 150-300 (o) C.