Stabilizing Au in a mixed-valence 3D halide perovskite.

Although Cu is ubiquitous, the relativistic destabilization of the 5d orbitals makes the isoelectronic Au exceedingly rare, typically stabilized only through Au-Au bonding or by using redox non-innocent ligands. Here we report the perovskite CsAuAuCl, an extended solid with mononuclear Au sites, which is stable to ambient conditions and characterized by single-crystal X-ray diffraction. The 2+ oxidation state of Au was assigned using Au Mössbauer spectroscopy, electron paramagnetic resonance, and magnetic susceptibility measurements, with comparison to paramagnetic and diamagnetic analogues with Cu and Pd, respectively, as well as to density functional theory calculations.

Directed assembly of layered perovskite heterostructures as single crystals.

The precise stacking of different two-dimensional (2D) structures such as graphene and MoS has reinvigorated the field of 2D materials, revealing exotic phenomena at their interfaces. These unique interfaces are typically constructed using mechanical or deposition-based methods to build a heterostructure one monolayer at a time. By contrast, self-assembly is a scalable technique, where complex materials can selectively form in solution.

Gold-Cage Perovskites: A Three-Dimensional Au-X Framework Encasing Isolated MX Octahedra (M = In, Sb, Bi; X = Cl, Br, I).

The CsAuMX (M = In, Sb, Bi; X = Cl, Br, I) perovskites are composed of corner-sharing Au-X octahedra that trace the edges of a cube containing an isolated M-X octahedron at its body center. This structure, unique within the halide perovskite family, may be derived from the doubled cubic perovskite unit cell by removing the metals at the cube faces. To our knowledge, these are the only halide perovskites where the octahedral sites do not bear an average 2+ charge.

Mechanochemical synthesis of an elusive fluorinated polyacetylene.

Polymer mechanochemistry has traditionally been employed to study the effects of mechanical force on chemical bonds within a polymer backbone or to generate force-responsive materials. It is under-exploited for the scalable synthesis of wholly new materials by chemically transforming the polymers, especially products inaccessible by other means. Here we utilize polymer mechanochemistry to synthesize a fluorinated polyacetylene, a long-sought-after air-stable polyacetylene that has eluded synthesis by conventional means.

Single Ensemble Non-exponential Photoluminescent Population Decays from a Broadband White-Light-Emitting Perovskite.

The mechanism of white-light emission from layered Pb-X (X = Cl or Br) perovskites following UV excitation has generated considerable interest. Prior time-dependent studies indicated that the broadband photoluminescence (PL) from (110) perovskites arises from a distribution of self-trapped excitonic sites emitting in different regions of the visible spectrum with different decay dynamics. Here, using time-correlated single photon counting to study single crystals, we show that the white-light emission decay from the (110) perovskite (EDBE)PbBr (EDBE = 2,2'-(ethylenedioxy)bis(ethylammonium)) behaves as a single ensemble.

Tuning the bandgap of CsAgBiBr through dilute tin alloying.

The promise of lead halide hybrid perovskites for optoelectronic applications makes finding less-toxic alternatives a priority. The double perovskite CsAgBiBr () represents one such alternative, offering long carrier lifetimes and greater stability under ambient conditions. However, the large and indirect 1.

Dynamically Disordered Lattice in a Layered Pb-I-SCN Perovskite Thin Film Probed by Two-Dimensional Infrared Spectroscopy.

The dynamically flexible lattices in lead halide perovskites may play important roles in extending carrier recombination lifetime in 3D perovskite solar-cell absorbers and in exciton self-trapping in 2D perovskite white-light phosphors. Two-dimensional infrared (2D IR) spectroscopy was applied to study a recently reported Pb-I-SCN layered perovskite. The Pb-I-SCN perovskite was spin-coated on a SiO surface as a thin film, with a thickness of ∼100 nm, where the SCN anions were isotopically diluted with the ratio of SCN:SCN = 5:95 to avoid vibrational coupling and excitation transfer between adjacent SCN anions.