Chemical Mapping of Excitons in Halide Double Perovskites.

Halide double perovskites comprise an emerging class of semiconductors with tremendous chemical and electronic diversity. While their band structure features can be understood from frontier-orbital models, chemical intuition for optical excitations remains incomplete. Here, we use ab initio many-body perturbation theory within the and the Bethe-Salpeter equation approach to calculate excited-state properties of a representative range of CsBB'Cl double perovskites.

Emergence of Rashba-/Dresselhaus effects in Ruddlesden-Popper halide perovskites with octahedral rotations.

Ruddlesden-Popper halide perovskites are highly versatile quasi-two-dimensional energy materials with a wide range of tunable optoelectronic properties. Here we use the all-inorganic Csn+1PbX3n+1Ruddlesden-Popper perovskites with X = I, Br, and Cl to systematically model the effect of octahedral tilting distortions on the energy landscape, band gaps, macroscopic polarization, and the emergence of Rashba-/Dresselhaus splitting in these materials. We construct all unique = 1 and = 2 structures following from octahedral tilts and use first-principles density functional theory to calculate total energies, polarizations and band structures, backed up by band gap calculations using theapproach.

Chemically Localized Resonant Excitons in Silver-Pnictogen Halide Double Perovskites.

Halide double perovskites with alternating silver and pnictogen cations are an emerging family of photoabsorber materials with robust stability and band gaps in the visible range. However, the nature of optical excitations in these systems is not yet well understood, limiting their utility. Here, we use many-body perturbation theory within the approximation and the Bethe-Salpeter equation approach to calculate the electronic structure and optical excitations of the double perovskite series CsAgBX, with B = Bi, Sb and X = Br, Cl.

Dimensional reduction of the small-bandgap double perovskite CsAgTlBr.

Quantum confinement effects in lower-dimensional derivatives of the ABX (A = monocation, X = halide) single perovskites afford striking optical and electronic changes, enabling applications ranging from solar absorbers to phosphors and light-emitting diodes. Halide double perovskites form a larger materials family, known since the late 1800s, but lower-dimensional derivatives remain rare and prior work has revealed a minimal effect of quantum confinement on their optical properties. Here, we synthesize three new lower-dimensional derivatives of the 3D double perovskite CsAgTlBr: 2D derivatives with mono- () and bi-layer thick () inorganic sheets and a quasi-1D derivative ().