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Low-dimensional hybrid organic-inorganic metal halides have received increased attention because of their outstanding optical and electronic properties. However, the most studied hybrid compounds contain lead and have long-term stability issues, which must be addressed for their use in practical applications. Here, we report a new zero-dimensional hybrid organic-inorganic halide, RInBr4, featuring photoemissive trimethyl(4-stilbenyl)methylammonium (R+) cations and nonemissive InBr4- tetrahedral anions. The crystal structure of RInBr4 is composed of alternating layers of inorganic anions and organic cations along the crystallographic a axis. The resultant hybrid demonstrates bright-blue emission with Commission Internationale de l'Eclairage color coordinates of (0.19, 0.20) and a high photoluminescence quantum yield (PLQY) of 16.36% at room temperature, a 2-fold increase compared to the PLQY of 8.15% measured for the precursor organic salt RBr. On the basis of our optical spectroscopy and computational work, the organic component is responsible for the observed blue emission of the hybrid material. In addition to the enhanced light emission efficiency, the novel hybrid indium bromide demonstrates significantly improved environmental stability. These findings may pave the way for the consideration of hybrid organic In(III) halides for light emission applications.

Recently, copper(I) halides have been gaining increased attention as highly luminescent nontoxic alternatives to lead halide perovskites for optoelectronic applications. Here, we report preparation...

Hybrid organic–inorganic halides containing Bi and Sb generally exhibit higher stability and lower toxicity compared to Pb analogues. In this work, the synthesis, crystal and electronic structures and optical properties of a brand-new methylammonium bismuth iodide, (MA)4Bi6I22 (MA+ = CH3NH3+), are reported. Interestingly, we find that the presence of the HgI2 is necessary for the targeted preparation of (MA)4Bi6I22. (MA)4Bi6I22 contains isolated [Bi6I22]4− clusters made of six edge-sharing octahedral BiI6 units, which are separated by MA+ cations in its 0D crystal structure. A relatively low optical band gap of 1.9 eV was estimated for (MA)4Bi6I22 based on diffuse reflectance measurements. An intense photoluminescence peak emerges at 636 nm at low temperatures that supports the assigned band gap value. Electronic structure calculations show the presence of flat bands in the valence and conduction bands, consistent with the low-dimensional structure of (MA)4Bi6I22, and slightly indirect nature of the bandgap. Our findings suggest that the use of facilitator moieties such as HgI2 may provide a pathway to obtaining alternative methylammonium bismuth iodides to (MA)3Bi2I9.

Inexpensive and highly efficient luminescent materials based on multinary halides have received increased attention in recent years. Among those considered most promising are the perovskites such a...

The photophysical mechanism of ultrabright visible light emission in the zero-dimensional (0D) hybrid organic–inorganic material (HOIM), (DETA)PbCl5·H2O (DETA = diethylenetriammonium), has been stu...

Perovskite solar cells have recently enabled power conversion efficiency comparable to established technologies such as silicon and cadmium telluride. Ongoing efforts to improve the stability of halide perovskites in ambient air has yielded promising results. However, the presence of toxic heavy element lead (Pb) remains a major concern requiring further attention. Herein, we report three new Pb-free hybrid organic-inorganic perovskite-type halides based on gold (Au), (CH3 NH3 )AuBr4 ⋅H2 O (1), (CH3 NH3 )AuCl4 ⋅H2 O (2), and (CH3 NH3 )AuCl4 (3). Hydrated compounds 1 and 2 crystallize in a brand-new structure type featuring perovskite-derived 2D layers and 1D chains based on pseudo-octahedral AuX6 building blocks. In contrast, the novel crystal structure of the solvent-free compound 3 shows an exotic non-perovskite quasi-2D layered structure containing edge- and corner-shared AuCl6 octahedra. The use of Au metal instead of Pb results in unprecedented low band gaps below 2.5 eV for single-layered metal chlorides and bromides. Moreover, at room temperature the three compounds show a weak blue emission due to the electronic transition between Au-6s and Au-5d, in agreement with the density function theory (DFT) calculation results. These findings are discussed in the context of viability of Au-based halides as alternatives for Pb-based halides for optoelectronic applications.

Low-dimensional hybrid organic–inorganic materials (HOIMs) are being widely investigated for their unique optoelectronic properties. Some of them exhibit broadband white-light (WL) luminescence upon UV excitation, providing a potential for the fabrication of single-component white-light-emitting diodes. Here, we report new examples of low-dimensional HOIMs, based on 4-aminopyridinium (4AMP) and group 12 metals (Hg and Zn), for single-component WL emission. The 4AMP cation containing structures feature HgBr4 and ZnBr4 isolated tetrahedra in (C5H7N2)2HgBr4·H2O (1) and (C5H7N2)2ZnBr4 (2), respectively. The presence of isolated molecular units in the zero-dimensional structures results in strongly localized charges and bright WL luminescence with corresponding Commission Internationale de l’Eclairage color coordinates of (0.34, 0.38) and (0.25, 0.26), correlated color temperatures of 5206 K (1) and 11 630 K (2), and very high color rendering indexes (CRI) of 87 (1) and 96 (2). The visibly bright WL emission a...

Recently, interest in developing efficient, low-cost, nontoxic, and stable metal halide emitters that can be incorporated into solid-state lighting technologies has taken hold. Here we report nonto...

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 Rb4Ag2BiBr9 prepared using the mixed-cation approach; however, Rb4Ag2BiBr9 adopts a new structure type (Pearson’s code oP32) featuring BiBr6 octahedra and AgBr5 square pyramids that share common edges and corners to form a unique 2D layered non-perovskite structure. Rb4Ag2BiBr9 is also demonstrated to be thermally stable with the measured onset decomposition temperature of To = 520 °C. Optical absorption measurements and density functional theory calculations suggest a nearly direct band gap for Rb4Ag2BiBr9. Room temperature p...

Ternary group 11 halides, especially those utilizing copper (I), have recently been explored as relatively non-toxic alternatives to the popular luminescent lead halide perovskites. This talk will focus on one such family, A2CuX3 (A=Rb+, K+; X= Cl-, Br-), which exhibit outstanding light emission properties, with up to unity photoluminescent quantum yields. These samples, along with other ternary group 11 halides, have been investigated through an in-depth optical characterization. The ultrabright photoluminescence in the studied group 11 halides is ascribed to self-trapped excitons localized on the [CuX3]2- anionic substructure based on density functional theory (DFT) calculations and optical spectroscopy results.

International audience; We report syntheses, crystal and electronic structures, and characterization of three new hybrid organic−inorganic halides (R)ZnBr 3 (DMSO), (R) 2 CdBr 4 · DMSO, and (R)CdI 3 (DMSO) (where (R) = C 6 (CH 3) 5 CH 2 N(CH 3) 3 , and DMSO = dimethyl sulfoxide). The compounds can be conveniently prepared as single crystals and bulk polycrystalline powders using a DMSO−methanol solvent system. On the basis of the single-crystal X-ray diffraction results carried out at room temperature and 100 K, all compounds have zero-dimensional (0D) crystal structures featuring alternating layers of bulky organic cations and molecular inorganic anions based on a tetrahedral coordination around group 12 metal cations. The presence of discrete molecular building blocks in the 0D structures results in localized charges and tunable room-temperature light emission, including white light for (R)ZnBr 3 (DMSO), bluish-white light for (R) 2 CdBr 4 ·DMSO, and green for (R)CdI 3 (DMSO). The highest photoluminescence quantum yield (PLQY) value of 3.07% was measured for (R)ZnBr 3 (DMSO), which emits cold white light based on the calculated correlated color temperature (CCT) of 11,044 K. All compounds exhibit fast photoluminescence lifetimes on the timescale of tens of nanoseconds, consistent with the fast luminescence decay observed in π-conjugated organic molecules. Temperature dependence photoluminescence study showed the appearance of additional peaks around 550 nm, resulting from the organic salt emission. Density functional theory calculations show that the incorporation of both the low-gap aromatic molecule R and the relatively electropositive Zn and Cd metals can lead to exciton localization at the aromatic molecular cations, which act as luminescence centers.

High temperature synthesis and optical band gaps are reported for three candidate photovoltaic earth-abundant Cu2PbSiS4, Ag2PbGeS4 and KAg2SbS4 semiconductors. The reported synthesis method is found to be more advantageous for KAg2SbS4 compared to the literature reported synthesis utilizing supercritical ammonia as a reaction medium, which produces a mixture of chalcogenide products. Based on optical diffuse reflectance data, Cu2PbSiS4, Ag2PbGeS4 and KAg2SbS4 have band gaps in the 1.6–1.8 eV range, and are shown to be stable in ambient air for a period of 6 weeks, making them attractive candidates for solar cell applications. Density functional theory (DFT) calculations indicate indirect band gaps for Cu2PbSiS4 and KAg2SbS4, and a nearly direct band gap for Ag2PbGeS4 with the calculated difference between indirect and direct gaps of only 30 meV. The p-type semiconducting behavior of Cu2PbSiS4, Ag2PbGeS4 is also verified by the transport measurments. The 3D connectivity of the polyanionic networks in these compounds results in dispersive valence and conduction bands, which is especially noticeable for KAg2SbS4. This fact is in part attributed to the presence of formally pentavalent SbV in this compound leading to empty Sb 5s orbitals in the conduction band. We discuss the potential of Cu2PbSiS4, Ag2PbGeS4 and KAg2SbS4 for photovoltaic applications based on synthesis, stability, band gap and electronic structure considerations.

We report synthesis, crystal and electronic structures, and optical properties of two new Hg-based zero-dimensional hybrid organic-inorganic halides (HIm)2Hg3Cl8 and (HIm)HgI3 (HIm = imidazolium). (HIm)2Hg3Cl8 crystallizes in the triclinic P-1 space group with a pseudo-layered structure made of organic imidazolium cation layers and anionic inorganic layers containing [Hg2Cl6]2- units and linear [HgCl2]0 molecules. (HIm)HgI3 crystallizes in the monoclinic P21/c space group featuring anionic [HgI3]- units that are surrounded by imidazolium cations. Based on density functional theory calculations, (HIm)2Hg3Cl8 has an indirect band gap, whereas (HIm)HgI3 has a direct band gap with the measured onsets of optical absorption at 3.43 and 2.63 eV, respectively. (HIm)2Hg3Cl8 and (HIm)HgI3 are broadband light emitters with broad photoluminescence peaks centered at 548 nm (2.26 eV) and 582 nm (2.13 eV), respectively. Following the crystal and electronic structure considerations, the PL peaks are assigned to self-trapped excitons.

We report the synthesis, crystal and electronic structures, as well as optical properties of the hybrid organic–inorganic compounds MA2CdX4 (MA = CH3NH3; X = Cl, Br, I). MA2CdI4 is a new compound, whereas, for MA2CdCl4 and MA2CdBr4, 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 MA2CdX4 solutions with optimized conditions yielding mm-sized colorless (X = Cl, Br) and pale yellow (X = I) crystals. Single crystal and variable temperature powder X-ray diffraction measurements suggest that MA2CdCl4 forms a 2D layered perovskite structure and has two structural transitions at 283 and 173 K. In contrast, MA2CdBr4 and MA2CdI4 adopt 0D K2SO4-derived crystal structures based on isolated CdX4 tetrahedra and show no phase transitions down to 20 K. The contrasting crystal structures and chemical compositions in the MA2CdX4 family impact their air stabilities, investigated...

Two new ternary manganese bismuthides have been synthesized and their structures established based on single-crystal X-ray diffraction methods. Sr2MnBi2 crystallizes in the orthorhombic space group Pnma (a = 16.200(9) A, b = 14.767(8) A, c = 8.438(5) A, V = 2018(2) A3; Z = 12; Pearson index oP60) and is isostructural to the antimonide Sr2MnSb2. The crystal structure contains corrugated layers of corner- and edge-shared [MnBi4] tetrahedra and Sr atoms enclosed between these layers. Electronic structure calculations suggest that Sr2MnBi2 is a magnetic semiconductor possessing Mn2+ (high-spin d5) ions, and its structure can be rationalized within the Zintl concept as [Sr2+]2[Mn2+][Bi3-]2. The temperature dependence of the resistivity shows behavior consistent with a degenerate semiconductor/poor metal, and magnetic susceptibility measurements reveal a high degree of frustration resulting from the two-dimensional nature of the structure. The compositionally similar Ba2Mn1-xBi2 (x ≈ 0.15) crystallizes in a very different structure (space group Imma, a = 25.597(8) A, b = 25.667(4) A, c = 17.128(3) A, V = 11253(4) A3; Z = 64; Pearson index oI316) with its own structure type. The complex structure boasts Mn atoms in a variety of coordination environments and can be viewed as consisting of two interpenetrating 3D frameworks, linked by Bi-Bi bonds. Ba2Mn1-xBi2 can be regarded as a highly reduced compound with anticipated metallic behavior.

Recent work has identified a non-zinc-blende-type quaternary semiconductor, Cu2BaSnS4–xSex (CBTSSe), as a promising candidate for thin-film photovoltaics (PVs). CBTSSe circumvents difficulties of competing PV materials regarding (i) toxicity (e.g., CdTe), (ii) scarcity of constituent elements (e.g., Cu(In,Ga)(S,Se)2/CdTe), and (iii) unavoidable antisite disordering that limits further efficiency improvement (e.g., in Cu2ZnSnS4–xSex). In this work, we build on the CBTSSe paradigm by computationally scanning for further improved, earth-abundant and environmentally friendly thin-film PV materials among the 16 quaternary systems I2–II–IV–VI4 (I = Cu, Ag; II = Sr, Ba; IV = Ge, Sn; VI = S, Se). The band structures, band gaps, and optical absorption properties are predicted by hybrid density-functional theory calculations. We find that the Ag-containing compounds (which belong to space groups I222 or I42m) show indirect band gaps. In contrast, the Cu-containing compounds (which belong to space group P31/P32 and...

Single crystals of ( Nd 1 − x Ce x ) 2 Fe 14 B , some reaching ∼ 6 × 8 × 8 mm 3 in volume, are grown out of Fe-(Nd, Ce) flux. This crystal growth method allows for large ( Nd 1 − x Ce x ) 2 Fe 14 B single crystals to be synthesized using a simple flux growth procedure. Chemical and structural analyses of the crystals indicate that ( Nd 1 − x Ce x ) 2 Fe 14 B forms a solid solution until at least x =0.38 with a Vegard-like variation of the lattice constants with x . Refinements of single crystal neutron diffraction data indicate that Ce has a slight site preference (7:3) for the 4 g rare earth site over the 4 f site. Magnetization measurements at 300 K show only small decreases with increasing Ce content in saturation magnetization ( M s ) and anisotropy field ( H A ), and Curie temperature ( T C ). First principles calculations are carried out to understand the effect of Ce substitution on the electronic and magnetic properties. For a multitude of applications, it is expected that the advantage of incorporating lower-cost and more abundant Ce will outweigh the small adverse effects on magnetic properties. Ce-substituted Nd 2 Fe 14 B is therefore a potential high-performance permanent magnet material with substantially reduced Nd content.

The magnetism in the sawtooth lattice of Mn in the olivine chalcogenides, ${\mathrm{Mn}}_{2}{\mathrm{SiS}}_{4\ensuremath{-}x}{\mathrm{Se}}_{x}$ ($x=1--4$), is studied in detail by analyzing their magnetization, specific heat, and thermal conductivity properties and complemented with density functional theory calculations. The air-stable chalcogenides are antiferromagnets and show a linear trend in the transition temperature ${T}_{N}$ as a function of Se content ($x$), which shows a decrease from ${T}_{N}\ensuremath{\approx}86\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ for ${\mathrm{Mn}}_{2}{\mathrm{SiS}}_{4}$ to 66 K for ${\mathrm{Mn}}_{2}{\mathrm{SiSe}}_{4}$. Additional magnetic anomalies are revealed at low temperatures for all the compositions. Magnetization irreversibilities are observed as a function of $x$. The specific heat and the magnetic entropy indicate the presence of short-range spin fluctuations in ${\mathrm{Mn}}_{2}{\mathrm{SiS}}_{4\ensuremath{-}x}{\mathrm{Se}}_{x}$. A spin-flop antiferromagnetic phase transition in the presence of applied magnetic field is present in ${\mathrm{Mn}}_{2}{\mathrm{SiS}}_{4\ensuremath{-}x}{\mathrm{Se}}_{x}$, where the critical field for the spin flop increases from $x=0$ towards 4 in a nonlinear fashion. Density functional theory calculations show that an overall antiferromagnetic structure with ferromagnetic coupling of the spins in the $ab$ plane minimizes the total energy. The band structures calculated for ${\mathrm{Mn}}_{2}{\mathrm{SiS}}_{4}$ and ${\mathrm{Mn}}_{2}{\mathrm{SiSe}}_{4}$ reveal features near the band edges similar to those reported for Fe-based olivines suggested as thermoelectrics; however the experimentally determined thermal transport data do not support superior thermoelectric features. The transition from long-range magnetic order in ${\mathrm{Mn}}_{2}{\mathrm{SiS}}_{4}$ to short-range order and spin fluctuations in ${\mathrm{Mn}}_{2}{\mathrm{SiSe}}_{4}$ is explained using the variation of the Mn-Mn distances in the triangle units that constitutes the sawtooth lattice upon progressive replacement of sulfur with selenium. Overall, the results presented here point towards the role played by magnetic anisotropy and geometric frustration in the antiferromagnetic state of the sawtooth olivines.

Perovskite solar cells have recently enabled power conversion efficiency comparable to established technologies such as silicon and cadmium telluride. Ongoing efforts to improve the stability of halide perovskites in ambient air has yielded promising results. However, the presence of toxic heavy element lead (Pb) remains a major concern requiring further attention. Herein, we report three new Pb-free hybrid organic-inorganic perovskite-type halides based on gold (Au), (CH

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 Rb

Chalcogenides such as CdTe, Cu(In,Ga)(S,Se)2 (CIGSSe), and Cu2ZnSn(S,Se)4 (CZTSSe) have enabled remarkable advances in thin-film photovoltaic performance, but concerns remain regarding (i) the toxicity (CdTe) and (ii) scarcity (CIGSSe/CdTe) of the constituent elements and (iii) the unavoidable antisite disordering that limits further efficiency improvement (CZTSSe). In this work, we show that a different materials class, the BaCu2SnSexS4–x (BCTSSe) system, offers a prospective path to circumvent difficulties (i–iii) and to target new environmentally friendly and earth-abundant absorbers. Antisite disordering and associated band tailing are discouraged in BCTSSe due to the distinct coordination environment of the large Ba2+ cation. Indeed, an abrupt absorption edge and sharp associated photoluminescence emission demonstrate a reduced impact of band tailing in BCTSSe relative to CZTSSe. Our combined experimental and computational studies of BCTSSe reveal that the compositions 0 ≤ x ≤ 4 exhibit a tunable nea...

Lead thiocyanate in the perovskite precursor can increase the grain size of a perovskite thin film and reduce the conductivity of the grain boundaries, leading to perovskite solar cells with reduced hysteresis and enhanced fill factor. A planar perovskite solar cell with grain boundary and interface passivation achieves a steady-state efficiency of 18.42%.

Although known since the late 19th century, organic-inorganic perovskites have recently received extraordinary research community attention because of their unique physical properties, which make them promising candidates for application in photovoltaic (PV) and related optoelectronic devices. This review will explore beyond the current focus on three-dimensional (3-D) lead(II) halide perovskites, to highlight the great chemical flexibility and outstanding potential of the broader class of 3-D and lower dimensional organic-based perovskite family for electronic, optical, and energy-based applications as well as fundamental research. The concept of a multifunctional organic-inorganic hybrid, in which the organic and inorganic structural components provide intentional, unique, and hopefully synergistic features to the compound, represents an important contemporary target.

In this work, we describe details of a two-step deposition approach that enables the preparation of continuous and well-structured thin films of Cs2SnI6, which is a one-half Sn-deficient 0-D perovskite derivative (i.e., the compound can also be written as CsSn0.5I3, with a structure consisting of isolated SnI64– octahedra). The films were characterized using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), UV–vis spectroscopy, photoluminescence (PL), photoelectron spectroscopy (UPS, IPES, XPS), and Hall effect measurements. UV–vis and PL measurements indicate that the obtained Cs2SnI6 film is a semiconductor with a band gap of 1.6 eV. This band gap was further confirmed by the UPS and IPES spectra, which were well reproduced by the calculated density of states with the HSE hybrid functional. The Cs2SnI6 films exhibited n-type conduction with a carrier density of 6(1) × 1016 cm–3 and mobility of 2.9(3) cm2/V·s. While the computationally derived band str...

We assess the viability for photovoltaic applications of proposed Pb-free perovskites with mixed chalcogen and halogen anions, AB(Ch,X)3 (A = Cs or Ba; B = Sb or Bi; Ch = chalcogen; X = halogen), by examining critical issues such as the structural, electronic/optical properties, and stability through the combination of density-functional theory calculations and solid-state reactions. The calculations show that these quaternary Pb-free perovskites are thermodynamically unstable—they are prone to decompose into ternary and/or binary secondary phases or form phases with nonperovskite structures. Solid-state synthesis efforts confirm the theoretically predicted difficulty for preparing these compounds; all attempted reactions do not form the desired perovskite phases with mixed chalcogen and halogen anions under conditions examined. Instead, they form separate binary and ternary compounds. Despite earlier predictions of promising characteristics for these prospective perovskites for photovoltaics, our results...

We explore the photovoltaic-relevant properties of the 2D MA2Pb(SCN)2I2 (where MA = CH3NH3(+)) perovskite using a combination of materials synthesis, characterization and density functional theory calculation, and determine electronic properties of MA2Pb(SCN)2I2 that are significantly different from those previously reported in literature. The layered perovskite with mixed-anions exhibits an indirect bandgap of ∼2.04 eV, with a slightly larger direct bandgap of ∼2.11 eV. The carriers (both electrons and holes) are also found to be confined within the 2D layers. Our results suggest that the 2D MA2Pb(SCN)2I2 perovskite may not be among the most promising absorbers for efficient single-junction solar cell applications; however, use as an absorber for the top cell of a tandem solar cell may still be a possibility if films are grown with the 2D layers aligned perpendicular to the substrates.

Through density functional theory calculations, we show that the alloy perovskite system BaZr1–xTixS3 (x 0) may not be stable under thermal equilibrium growth conditions. Calculations of decomposition energies suggest that introducing compressive strain may be a plausible approach to stabilize BaZr1–xTixS3 thin films.

Investigation of the quaternary system, Ca&ndash, Eu&ndash, Cd&ndash, Sb, led to a discovery of the new solid solutions, Ca1&minus, xEuxCd2Sb2, with the CaAl2Si2 structure type (x &asymp, 0.3&ndash, 0.9, hP5, P 3 &macr, m1, a = 4.6632(5)&ndash, 4.6934(3) &Aring, c = 7.630(1)&ndash, 7.7062(7) &Aring, ), Ca2&minus, xEuxCdSb2 with the Yb2CdSb2 type (x &asymp, 0.6, oS20, Cmc21, a = 4.646(2) &Aring, b = 17.733(7) &Aring, c = 7.283(3) &Aring, ), and Eu11&minus, xCaxCd6Sb12 with the Sr11Cd6Sb12 type (x &asymp, 1, mS58, C2/m, a = 32.407(4) &Aring, b = 4.7248(5) &Aring, c = 12.377(1) &Aring, &beta, = 109.96(1)&deg, ). Systematic crystallographic studies of the Ca1&minus, xEuxCd2Sb2 series indicated expansion of the unit cell upon an increase in the Eu content, in accordance with a larger ionic radius of Eu2+ vs. Ca2+. The Ca2&minus, xEuxCdSb2 composition with x &asymp, 0.6 adopts the non-centrosymmetric space group, Cmc21, although the parent ternary phase, Ca2CdSb2, crystallizes in the centrosymmetric space group, Pnma. Two non-equivalent Ca sites in the layered crystal structure of Ca2&minus, xEuxCdSb2 get unevenly occupied by Eu, with a preference for the interlayer position, which offers a larger available volume. Similar size-driven preferred occupation is observed in the Eu11&minus, xCaxCd6Sb12 solid solution with x &asymp, 1.

Computational, thin-film deposition, and characterization approaches have been used to examine the ternary halide semiconductor Cs3Sb2I9. Cs3Sb2I9 has two known structural modifications, the 0-D dimer form (space group P63/mmc, no. 194) and the 2-D layered form (P3m1, no. 164), which can be prepared via solution and solid-state or gas-phase reactions, respectively. Our computational investigations suggest that the layered form, which is a one-third Sb-deficient derivative of the ubiquitous perovskite structure, is a potential candidate for high-band gap photovoltaic (PV) applications. In this work, we describe details of a two-step deposition approach that enables the preparation of large grain (>1 μm) and continuous thin films of the lead-free layered perovskite derivative Cs3Sb2I9. Depending on the deposition conditions, films that are c-axis oriented or randomly oriented can be obtained. The fabricated thin films show enhanced stability under ambient air, compared to methylammonium lead(II) iodide per...

Lattice distortions corresponding to Ba displacements with respect to the FeAs sublattice are revealed to break the room-temperature tetragonal symmetry in Ba(Fe1-x Cox)2 As2. The displacements yield twin domains of the size of ≈10 nm. The domain size correlates with the magnitude of the local Fe magnetic moment and its non-monotonic dependence on Co concentration.

We report the synthesis, crystal and electronic structures, as well as optical properties of the hybrid organic-inorganic compounds MA

Two new ternary manganese bismuthides have been synthesized and their structures established based on single-crystal X-ray diffraction methods. Sr

Through high temperature synthesis at 1300 °C and above, our group has discovered and characterized the novel CaRE3SbO4 and Ca2RE8Sb3O10 phases (RE = Ce–Nd, Sm–Dy for CaRE3SbO4, RE = La–Nd, Sm–Dy for Ca2RE8Sb3O10). This result was motivated by the idea of opening a band gap and introducing structural complexity in the rare-earth antimonide framework by incorporation of rare-earth oxide and calcium oxide. The CaRE3SbO4 phases adopt the tetragonal I4/m symmetry while the Ca2RE8Sb3O10 ones adopt the monoclinic C2/m symmetry. These structures show many similarities to the other RE–Sb–O phases discovered recently, particularly to the RE3SbO3 and RE8Sb3O8 phases, in which a prolonged heat treatment results in one structure converting to another by elongation of the rare-earth oxide slabs. Electrical resistivity measurements yielded semiconducting properties for both series, despite the unbalanced electron count for Ca2RE8Sb3O10 and electronic structure calculations that support metallic-type conduction. This un...

Polycrystalline BaCu2SnSexS4-x (x = 0, 1, 2, 3, 4) samples are prepared by solid state reaction of stoichiometric amounts of BaS, SnS, CuS, BaSe, SnSe, and CuSe (evacuated quartz tubes, 650 °C10—15 h).

We present a study of the tetragonal to collapsed-tetragonal transition of ${\mathrm{CaFe}}_{2}{\mathrm{As}}_{2}$ using angle-resolved photoemission spectroscopy and dynamical mean field theory-based electronic structure calculations. We observe that the collapsed-tetragonal phase exhibits reduced correlations and a higher coherence temperature due to the stronger Fe-As hybridization. Furthermore, a comparison of measured photoemission spectra and theoretical spectral functions shows that momentum-dependent corrections to the density functional band structure are essential for the description of low-energy quasiparticle dispersions. We introduce those using the recently proposed combined ``screened exchange + dynamical mean field theory'' scheme.

We report the synthesis of ternary barium copper pnictides, Ba2Cu3P4 and BaCu2Pn2 (Pn=As, Sb), and their structural, magnetic, and transport properties. They all crystallize in different structures shown by X-ray diffraction, although their structures reveal close relations. The body-centered tetragonal BaCu2As2 adopts ThCr2Si2-type (I4/mmm) structure, whereas Ba2Cu3P4 is a copper-deficient derivative of this phase, crystallizing in the body-centered orthorhombic space group, Ibam. There are two polymorphs of BaCu2Sb2: α-BaCu2Sb2 that adopts CaBe2Ge2-type structure; β-BaCu2Sb2 that is a 2:1 combination of CaBe2Ge2- and ThCr2Si2-type structural segments. All phases are metallic and non-magnetic. The room temperature thermal conductivity for polycrystalline BaCu2As2 is ≈ 2 W/(m K) and the Seebeck coefficient is ≈ 15 μV/K, which result in a small (≈0.03) thermoelectric figure of merit.

The new intermetallic compounds Sr2ZnP2, Sr2 ZnAs2, A2ZnSb2 and A2ZnBi2 (A = Sr, Eu) have been synthesized from the corresponding elements through high-temperature reactions using the flux-growth method. Their structures have been established by singlecrystal and powder X-ray diffraction. In all cases, the X-ray diffraction patterns can be successfully indexed based on hexagonal cells in the space group P63/mmc (no. 194) with lattice parameters in the range a = 4.31 4.73 and c = 7.9 8.55 . The average structure can be described in the ZrBeSi type (Pearson symbol hP6; 3 unique positions) with defects on the zinc site structure refinements indicate that every second zinc position is vacant, i.e., their formula unit is AZn1 xPn with x = 0.5 (A = Sr, Eu; Pn = P, As, Sb, Bi). No stoichiometry breadth was observed, which could imply that a super-structure with a long-range order of the zinc vacancies is plausible and evidence for such was sought using electron diffraction. The results from these experiments, as well as magnetic susceptibility measurements and band structure calculations using the LMTO code are also discussed.

Presented are the details of the syntheses, crystal and electronic structures of a new family of Zintl phases Na2ACdSb2 and K2ACdSb2 (A=Ca, Sr, Ba, Eu, Yb), as well as the solid solutions Sr2–xAxCdSb2, Ba2–xAxCdSb2 and Eu2–xYbxCdSb2. The structures of Na2ACdSb2 and K2ACdSb2 (A=Ca, Sr, Ba, Eu, Yb) were determined to be of a new type with the non-centrosymmetric space group Pmc21 (no. 26), Pearson symbol oP12, with lattice parameters a=4.684(1)−4.788(1) A; b=9.099(3)−9.117(2) A; c=7.837(1)−8.057(2) A for the Na2ACdSb2 series, and a=4.6637(9)−5.0368(8) A; b=9.100(2)−9.8183(15) A; and c=7.7954(15)−8.4924(13) A for K2ACdSb2, respectively. The solid solutions Sr2–xAxCdSb2, Ba2–xAxCdSb2 and Eu2–xYbxCdSb2 (x≈1) are isostructural and isoelectronic to the recently reported Yb2CdSb2 (space group Cmc21 (no. 36), Pearson symbol cP20). All discussed structures are based upon CdSb24– polyanionic layers, similar to the ones observed in Yb2CdSb2, with various alkali- and/or alkaline-earth cations coordinated to them. Magnetic susceptibility and Seebeck coefficient measurements on selected Eu2–xYbxCdSb2 samples, taken at low temperatures up to 300 K, are also reported.

We report millimeter-sized Nd5Pb3 single crystals grown out of a Nd-Co flux. We experimentally study the magnetic order of Nd5Pb3 single crystals by measuring the anisotropic magnetic properties, electrical resistivity under high pressure up to 8 GPa, specific heat, and neutron single crystal diffraction. Two successive magnetic orders are observed at T N1 = 44 K and T N2 = 8 K. The magnetic cells can be described with a propagation vector [Formula: see text]. Cooling below T N1, Nd1 and Nd3 order forming ferromagnetic stripes along the b-axis, and the ferromagnetic stripes are coupled antiferromagnetically along the a-axis for the [Formula: see text] magnetic domain. Cooling below T N2, Nd2 orders antiferromagnetically to nearby Nd3 ions. All ordered moments align along the crystallographic c-axis. The magnetic order at T N1 is accompanied by a quick drop of electrical resistivity upon cooling and a lambda-type anomaly in the temperature dependence of specific heat. At T N2, no anomaly was observed in electrical resistivity but there is a weak feature in specific heat. The resistivity measurements under hydrostatic pressures up to 8 GPa suggest a possible phase transition around 6 GPa. Our first-principles band structure calculations show that Nd5Pb3 has the same electronic structure as does Y5Si3 which has been reported to be a one-dimensional electride with anionic electrons that do not belong to any atom. Our study suggests that R 5Pb3 (R = rare earth) can be a materials playground for the study of magnetic electrides. This deserves further study after experimental confirmation of the presence of anionic electrons.

The isostructural and isoelectronic Zintl phases KA2Cd2Sb3 (A = Ca, Sr, Ba, Eu, Yb) are the first in the corresponding quaternary systems. They have been synthesized by high-temperature reactions of the respective elements and their structures have been established by single-crystal X-ray diffraction. The orthorhombic structure (space group Pnma, no. 62, Z = 4) is complex and is best described following the Zintl formalism as a channel-like three-dimensional ∞ 3 [Cd2Sb3]5− framework, with K+ and A2+ cations filling the space within it. The polyanionic framework is based on corner-shared antimony-tetrahedra, centered by the Cd. Electronic structures calculations using the linear muffin-tin orbital (LMTO) method suggest that the title compounds are electron-precise Zintl phases, evidenced by the small energy gaps at the Fermi level. Magnetic susceptibility data for KEu2Cd2Sb3, confirming divalent Eu are also presented.

Two new Zintl compounds Ba2Cd2As3 and Ba2Cd2Sb3 have been synthesized and structurally characterized. They crystallize in a novel monoclinic structure type with the space group C2/m (no. 12), featuring polyanionic layers made of CdPn4 tetrahedra (Pn = As, Sb) and homoatomic Pn–Pn bonds. The topological relationships between the structure of Ba2Cd2Sb3 and those of BaCd2Sb2 (CaAl2Si2 type) and Ba3Cd2Sb4 (own type) are discussed as well. Based on electronic structures calculations, carried out by the density-functional method, and resistivity measurements, pure Ba2Cd2As3 is shown to be a small-gap semiconductor and pure Ba2Cd2Sb3 to be a poor metal. The structures of the title compounds are amenable to doping on both cation and pnicogen sites, which could enable fine-tuning the transport properties, and make them promising materials for thermoelectric applications.

Reported are the synthesis of the new ternary compound Ba3Cd2Sb4 and its structure determination by single-crystal X-ray diffraction. Ba3Cd2Sb4 crystallizes with the monoclinic space group C2/m (No. 12); unit cell parameters a = 17.835(2) A, b = 4.8675(5) A, c = 7.6837(7) A, and beta = 112.214(1) degrees; Z = 4. Its structure can be viewed as made of Ba2+ cations and [Cd2Sb4] double chains that are interconnected through Sb-Sb bonds to form 2D infinity2[Cd2Sb4]6- layers. The bonding arrangement in Ba3Cd2Sb4 can also be derived from other known structure types that feature similar fragments, such as TiNiSi, Ca3AlAs3, and Ca5Al2Sb6. Tight-binding linear muffin-tin-orbital band structure calculations are presented as well and show that the constituent elements have closed-shell configurations, indicative of Ba3Cd2Sb4 being a Zintl phase with poor metallic behavior. Crystal orbital Hamilton population analyses on selected atomic interactions in this structure are discussed within the context of the site preference, manifested in the mixed-cation compounds and Ba3-xAxCd2Sb4, where A = Ca, Sr, Eu, and Yb.

Reported are the syntheses, crystal structure determinations from single-crystal X-ray diffraction, and magnetic properties of two new ternary compounds, Eu{sub 11}Cd{sub 6}Sb{sub 12} and Eu{sub 11}Zn{sub 6}Sb{sub 12}. Both crystallize with the complex Sr{sub 11}Cd{sub 6}Sb{sub 12} structure type-monoclinic, space group C2/m (no. 12), Z=2, with unit cell parameters a=31.979(4) A, b=4.5981(5) A, c=12.3499(14) A, {beta}=109.675(1){sup o} for Eu{sub 11}Zn{sub 6}Sb{sub 12}, and a=32.507(2) A, b=4.7294(3) A, c=12.4158(8) A, {beta}=109.972(1){sup o} for Eu{sub 11}Cd{sub 6}Sb{sub 12}. Their crystal structures are best described as made up of polyanionic {sub {infinity}}{sup 1}[Zn{sub 6}Sb{sub 12}]{sup 22-} and {sub {infinity}}{sup 1}[Cd{sub 6}Sb{sub 12}]{sup 22-} ribbons of corner-shared ZnSb{sub 4} and CdSb{sub 4} tetrahedra and Eu{sup 2+} cations. A notable characteristic of these structures is the presence of Sb-Sb interactions, which exist between two tetrahedra from adjacent layers, giving rise to unique channels. Detailed structure analyses shows that similar bonding arrangements are seen in much simpler structure types, such as Ca{sub 3}AlAs{sub 3} and Ca{sub 5}Ga{sub 2}As{sub 6} and the structure can be rationalized as their intergrowth. Temperature-dependent magnetization measurements indicate that Eu{sub 11}Cd{sub 6}Sb{sub 12} orders anti-ferromagnetically below 7.5 K, while Eu{sub 11}Zn{sub 6}Sb{sub 12} does not order down to 5 K. Resistivity measurementsmore » confirm that Eu{sub 11}Cd{sub 6}Sb{sub 12} is poorly metallic, as expected for a Zintl phase. - Graphical abstract: The synthesis, structure determination from single-crystal X-ray diffraction and magnetic properties of Eu{sub 11}Zn{sub 6}Sb{sub 12} and Eu{sub 11}Cd{sub 6}Sb{sub 12} are reported. Both compounds crystallize with the monoclinic space group C2/m, and their structure can be viewed as built of ZnSb{sub 4} or CdSb{sub 4} tetrahedra, which are connected through common corners and exo-bonds.« less