Gold-Cage Perovskites: A Three-Dimensional Au^III–X Framework Encasing Isolated MX₆^3– Octahedra (M^III = In, Sb, Bi; X = Cl^–, Br^–, I^–)

Abstract

The Cs8AuIII 4MIIIX23 (M = In3+, Sb3+, Bi3+; 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. Charge compensation in these materials requires a stoichiometric halide vacancy, which is disordered around the Au atom at the unit-cell corner and orders when the crystallization is slowed. Using X-ray crystallography, X-ray absorption spectroscopy, and pair distribution function analysis, we elucidate the structure of this unusual perovskite. Metal-site alloying produces further intricacies in this structure, which our model explains. Compared to other halide perovskites, this class of materials shows unusually low absorption onset energies ranging between ca. 1.0 and 2.4 eV. Partial reduction of Au3+ to Au+ affords an intervalence charge-transfer band, which redshifts the absorption onset of Cs8Au4InCl23 from 2.4 to 1.5 eV. With connected Au–X octahedra and isolated M–X octahedra, this structure type combines zero- and three-dimensional metal-halide sublattices in a single material and stands out among halide perovskites for its ordering of homovalent metals, ordering of halide vacancies, and incorporation of purely trivalent metals at the octahedral sites.

Gold-Based Double Perovskite-Related Polymorphs: Low Dimensional with an Ultranarrow Bandgap

“…Historical development of Au-based DPs (MA = methylammonium, FA = formamidinium, Qu = quinolone, PY = pyridine, GUA = guanidinium, DMA = dimethylammonium, IMD = imidazolium, and PIP = piperizinium). , …”

Dexter Energy Transfer in Zero-Dimensional Inorganic Metal Halides for Obtaining Near-Unity PLQY via Sb3+/Mn2+ Codoping

“…1−8 In these materials, a metal halide ionic octahedron is the fundamental building block and functional unit. 9,10 Thanks to the high tolerance of the perovskite lattice, many types of ions (and even vacancies) with different valence states can be assembled together to form a high-entropy and complex structure based on the principle of charge balance. 11,12 Theoretically, various physical properties can be obtained by the rational design of a combination of different functional units.…”

“…11,12 Theoretically, various physical properties can be obtained by the rational design of a combination of different functional units. 9,13,14 In solid-state lighting, the emergence of multidoping strategies has provided more choices for obtaining tunable white light in a single component. 13 In a metal halide perovskite host, the distance between the optical dopants is one of the most critical factors in extrinsic photoluminescence (PL).…”

“…Metal halide perovskites have been recently established as an unparalleled class of materials for light-harvesting and light-emitting applications because they have outstanding optoelectronic properties and can be easily processed in solution. − In these materials, a metal halide ionic octahedron is the fundamental building block and functional unit. , Thanks to the high tolerance of the perovskite lattice, many types of ions (and even vacancies) with different valence states can be assembled together to form a high-entropy and complex structure based on the principle of charge balance. , Theoretically, various physical properties can be obtained by the rational design of a combination of different functional units. ,, In solid-state lighting, the emergence of multidoping strategies has provided more choices for obtaining tunable white light in a single component …”

Design and defect study of Cs2AgBiBr6 double perovskite solar cell using suitable charge transport layers

“…Bi-based perovskites have excellent optoelectronic characteristics. Due to the positive three-valence state of bismuth, the stable phase is A 2 B 2 X 6 instead of ABX 3 , and MA + or Cs + has been integrated into the bismuth (Bi) halogens as an A-site cation [6]. In order to retain the 3D structure with a comparatively small bandgap, monovalent cations such as Ag + have been incorporated into bismuth iodide [7].…”