Near-Unity Light-Matter Interaction in Mid-Infrared van der Waals Metasurfaces.

Accessing mid-infrared radiation is of great importance for a range of applications, including thermal imaging, sensing, and radiative cooling. Here, we study light interaction with hexagonal boron nitride (hBN) nanocavities and reveal strong and tunable resonances across its hyperbolic transition. In addition to conventional phonon-polariton excitations, we demonstrate that the high refractive index of hexagonal boron nitride outside the Reststrahlen band allows enhanced light-matter interactions in deep subwavelength (<λ/15) nanostructures across a broad 7-8 μm range.

Temperature-Dependent Carrier Extraction and the Effects of Excitons on Emission and Photovoltaic Performance in CsFAMAPb(IBr) Solar Cells.

The photovoltaic parameters of triple cation perovskite [CsFAMAPb(IBr)] solar cells are investigated focusing on the electro-optical properties and differences in performance at low and high temperatures. The signature of a parasitic barrier to carrier extraction is observed at low temperatures, which results in a loss of performance at < 200 K. Intensity-dependent measurements indicate extraction across this parasitic interface is limited by a combination of the exciton binding energy and thermionic emission.

Hot-carrier dynamics in InAs/AlAsSb multiple-quantum wells.

A type-II InAs/AlAs[Formula: see text]Sb[Formula: see text] multiple-quantum well sample is investigated for the photoexcited carrier dynamics as a function of excitation photon energy and lattice temperature. Time-resolved measurements are performed using a near-infrared pump pulse, with photon energies near to and above the band gap, probed with a terahertz probe pulse. The transient terahertz absorption is characterized by a multi-rise, multi-decay function that captures long-lived decay times and a metastable state for an excess-photon energy of [Formula: see text] meV.

RbAgBiBr: A Lead-Free Visible Light Absorbing Halide Semiconductor with Improved Stability.

Replacement of the toxic heavy element lead in metal halide perovskites has been attracting a great interest because the high toxicity and poor air stability are two of the major barriers for their widespread utilization. Recently, mixed-cation double perovskite halides, also known as elpasolites, were proposed as an alternative lead-free candidate for the design of nontoxic perovskite solar cells. Herein, we report a new nontoxic and air stable lead-free all-inorganic semiconductor RbAgBiBr prepared using the mixed-cation approach; however, RbAgBiBr adopts a new structure type (Pearson's code oP32) featuring BiBr octahedra and AgBr square pyramids that share common edges and corners to form a unique 2D layered non-perovskite structure.

Enhanced hot electron lifetimes in quantum wells with inhibited phonon coupling.

Hot electrons established by the absorption of high-energy photons typically thermalize on a picosecond time scale in a semiconductor, dissipating energy via various phonon-mediated relaxation pathways. Here it is shown that a strong hot carrier distribution can be produced using a type-II quantum well structure. In such systems it is shown that the dominant hot carrier thermalization process is limited by the radiative recombination lifetime of electrons with reduced wavefunction overlap with holes.

Synthesis, Crystal and Electronic Structures, and Optical Properties of (CHNH)CdX (X = Cl, Br, I).

We report the synthesis, crystal and electronic structures, as well as optical properties of the hybrid organic-inorganic compounds MACdX (MA = CHNH; X = Cl, Br, I). MACdI is a new compound, whereas, for MACdCl and MACdBr, structural investigations have already been conducted but electronic structures and optical properties are reported here for the first time. Single crystals were grown through slow evaporation of MACdX solutions with optimized conditions yielding mm-sized colorless (X = Cl, Br) and pale yellow (X = I) crystals.