Showing papers on "Single crystal published in 2016"
TL;DR: The phosphorus-doped hexagonal tubular carbon nitride with the layered stacking structure was obtained from a hexagonal rod-like single crystal supramolecular precursor (monoclinic, C2/m) with a high hydrogen evolution rate and an apparent quantum efficiency better than most of bulk g-C3 N4 reported.
Abstract: Phosphorus-doped hexagonal tubular carbon nitride (P-TCN) with the layered stacking structure was obtained from a hexagonal rod-like single crystal supramolecular precursor (monoclinic, C2/m). The production process of P-TCN involves two steps: 1) the precursor was prepared by self-assembly of melamine with cyanuric acid from in situ hydrolysis of melamine under phosphorous acid-assisted hydrothermal conditions; 2) the pyrolysis was initiated at the center of precursor under heating, thus giving the hexagonal P-TCN. The tubular structure favors the enhancement of light scattering and active sites. Meanwhile, the introduction of phosphorus leads to a narrow band gap and increased electric conductivity. Thus, the P-TCN exhibited a high hydrogen evolution rate of 67 μmol h−1 (0.1 g catalyst, λ >420 nm) in the presence of sacrificial agents, and an apparent quantum efficiency of 5.68 % at 420 nm, which is better than most of bulk g-C3N4 reported.
876 citations
TL;DR: The phase transition of FAPbI3 between the α-phase and δ-phase is studied and photodetectors based on single-crystal FAP bI3 are demonstrated.
Abstract: 5 mm-scale large FAPbI 3 single crystals and corresponding photoconductive properties are shown. The phase transition of FAPbI3 between the α-phase and δ-phase is studied. The carrier mobility is 4.4 cm(2) V(-1) s(-1) with a lifetime of 484 ns in the bulk of the single crystal. Finally, photodetectors based on single-crystal FAPbI3 are demonstrated.
694 citations
TL;DR: The nontemplated colloidal synthesis of single crystal CsPbBr3 perovskite nanosheets with lateral sizes up to a few micrometers and with thickness of just a few unit cells is reported in the strong quantum confinement regime.
Abstract: We report the nontemplated colloidal synthesis of single crystal CsPbBr3 perovskite nanosheets with lateral sizes up to a few micrometers and with thickness of just a few unit cells (i.e., below 5 nm), hence in the strong quantum confinement regime, by introducing short ligands (octanoic acid and octylamine) in the synthesis together with longer ones (oleic acid and oleylamine). The lateral size is tunable by varying the ratio of shorter ligands over longer ligands, while the thickness is mainly unaffected by this parameter and stays practically constant at 3 nm in all the syntheses conducted at short-to-long ligands volumetric ratio below 0.67. Beyond this ratio, control over the thickness is lost and a multimodal thickness distribution is observed.
416 citations
TL;DR: In this article, the electronic structure and bonding characteristics of borophene were investigated by first-principles calculations, and the obtained optical properties exhibited strong anisotropy as well.
Abstract: Borophene (a two-dimensional boron sheet) is a new type of two-dimensional material, which was recently grown successfully on single crystal Ag substrates. In this paper, we investigate the electronic structure and bonding characteristics of borophene by first-principles calculations. The band structure of borophene shows highly anisotropic metallic behaviour. The obtained optical properties of borophene exhibit strong anisotropy as well. Finally, the thermodynamic properties are investigated based on the phonon properties.
321 citations
TL;DR: High-pressure PL data indicate that compression can mitigate this PL redshift and may afford higher steady-state voltages from these absorbers and show that pressure can significantly alter the transport and thermodynamic properties of these technologically important semiconductors.
Abstract: We report the first high-pressure single-crystal structures of hybrid perovskites. The crystalline semiconductors (MA)PbX3 (MA = CH3NH3+, X = Br– or I–) afford us the rare opportunity of understanding how compression modulates their structures and thereby their optoelectronic properties. Using atomic coordinates obtained from high-pressure single-crystal X-ray diffraction we track the perovskites’ precise structural evolution upon compression. These structural changes correlate well with pressure-dependent single-crystal photoluminescence (PL) spectra and high-pressure bandgaps derived from density functional theory. We further observe dramatic piezochromism where the solids become lighter in color and then transition to opaque black with compression. Indeed, electronic conductivity measurements of (MA)PbI3 obtained within a diamond-anvil cell show that the material’s resistivity decreases by 3 orders of magnitude between 0 and 51 GPa. The activation energy for conduction at 51 GPa is only 13.2(3) meV, su...
315 citations
TL;DR: It is demonstrated that the surface recombination rate (or surface trap state density) in methylammonium lead tribromide (MAPbBr3) single crystals can be fully and reversibly controlled by the physisorption of oxygen and water molecules, leading to a modulation of the photoluminescence intensity by over two orders of magnitude.
Abstract: One of the limiting factors to high device performance in photovoltaics is the presence of surface traps. Hence, the understanding and control of carrier recombination at the surface of organic-inorganic hybrid perovskite is critical for the design and optimization of devices with this material as the active layer. We demonstrate that the surface recombination rate (or surface trap state density) in methylammonium lead tribromide (MAPbBr3) single crystals can be fully and reversibly controlled by the physisorption of oxygen and water molecules, leading to a modulation of the photoluminescence intensity by over two orders of magnitude. We report an unusually low surface recombination velocity of 4 cm/s (corresponding to a surface trap state density of 108 cm−2) in this material, which is the lowest value ever reported for hybrid perovskites. In addition, a consistent modulation of the transport properties in single crystal devices is evidenced. Our findings highlight the importance of environmental conditions on the investigation and fabrication of high-quality, perovskite-based devices and offer a new potential application of these materials to detect oxygen and water vapor.
296 citations
TL;DR: In this paper, a single crystal platinum diselenide (PtSe2 ) nanosheets are synthesized using H2 PtCl6 and Se as the precursors.
Abstract: Ultrathin single crystal platinum diselenide (PtSe2 ) nanosheets are synthesized using H2 PtCl6 and Se as the precursors. The electronic properties are first investigated and exhibit p-type transport behavior with the mobility much larger than 7 cm2 V-1 s-1 . The further investigation on PtSe2 /MoS2 var der Waals p-n junction demonstrated that PtSe2 could be potentially applied in 2D electronics.
278 citations
TL;DR: It is revealed that light could greatly reduce the ion migration energy barrier in both polycrystalline and single crystalline OIHP, which is much shorter than what it was thought to take.
Abstract: Understanding the influence of light on ion migration in organic–inorganic halide perovskite (OIHP) materials is important to understand the photostability of perovskite solar cells. We reveal that light could greatly reduce the ion migration energy barrier in both polycrystalline and single crystalline OIHP. The activation energies derived from conductivity measurement under 0.25 Sun decrease to less than one half of the values in the dark. A typical ion drift velocity in CH3NH3PbI3 polycrystalline films is 1.2 μm s−1 under 1 Sun, compared with 0.016 μm s−1 under 0.02 Sun. Ion migration across the photoactive layers in most OIHP devices thus takes only subseconds under 1 Sun illumination, which is much shorter than what it was thought to take. Most important of all, ion migration through a single crystal surface is still too slow to be observed even after illumination for two days due to the large ion diffusion activation energy, >0.38 eV.
277 citations
TL;DR: In this paper, an all-optical study is presented that clearly distinguishes the surface kinetics from those of the bulk in the representative methylammonium-lead bromide (MAPbBr3) and -lead iodide(MAPbI3) single crystals.
Abstract: Organic–inorganic halide perovskite single crystals possess many outstanding properties conducive for photovoltaic and optoelectronic applications. However, a clear photophysics picture is still elusive, particularly, their surface and bulk photophysics are inexorably convoluted by the spectral absorbance, defects, coexisting photoexcited species, etc. In this work, an all-optical study is presented that clearly distinguishes the surface kinetics from those of the bulk in the representative methylammonium-lead bromide (MAPbBr3) and -lead iodide (MAPbI3) single crystals. It is found that the bulk recombination lifetime of the MAPbBr3 single crystal is shortened significantly by approximately one to two orders (i.e., from ≈34 to ≈1 ns) at the surface with a surface recombination velocity of around 6.7 × 103 cm s−1. The surface trap density is estimated to be around 6.0 × 1017 cm−3, which is two orders larger than that of the bulk (5.8 × 1015 cm−3). Correspondingly, the diffusion length of the surface excited species is ≈130–160 nm, which is considerably reduced compared to the bulk value of ≈2.6–4.3 μm. Furthermore, the surface region has a wider bandgap that possibly arises from the strong lattice deformation. The findings provide new insights into the intrinsic photophysics essential for single crystal perovskite photovoltaics and optoelectronic devices.
260 citations
Columbia University1, Rice University2, University of Texas at Austin3, Sandia National Laboratories4, Sungkyunkwan University5, University of Central Florida6, Hong Kong University of Science and Technology7, Harvard University8, Texas Instruments9, Ulsan National Institute of Science and Technology10
TL;DR: This work demonstrates that in an oxygen-activated chemical vapour deposition (CVD) process, half-millimetre size, Bernal-stacked BLG single crystals can be synthesized on Cu and discovers new microscopic steps governing the growth of the 2nd graphene layer below the 1st layer.
Abstract: Large, bilayer graphene single crystals can be grown by oxygen-activated chemical vapour deposition. Bernal (AB)-stacked bilayer graphene (BLG) is a semiconductor whose bandgap can be tuned by a transverse electric field, making it a unique material for a number of electronic and photonic devices1,2,3. A scalable approach to synthesize high-quality BLG is therefore critical, which requires minimal crystalline defects in both graphene layers4,5 and maximal area of Bernal stacking, which is necessary for bandgap tunability6. Here we demonstrate that in an oxygen-activated chemical vapour deposition (CVD) process, half-millimetre size, Bernal-stacked BLG single crystals can be synthesized on Cu. Besides the traditional ‘surface-limited’ growth mechanism for SLG (1st layer), we discovered new microscopic steps governing the growth of the 2nd graphene layer below the 1st layer as the diffusion of carbon atoms through the Cu bulk after complete dehydrogenation of hydrocarbon molecules on the Cu surface, which does not occur in the absence of oxygen. Moreover, we found that the efficient diffusion of the carbon atoms present at the interface between Cu and the 1st graphene layer further facilitates growth of large domains of the 2nd layer. The CVD BLG has superior electrical quality, with a device on/off ratio greater than 104, and a tunable bandgap up to ∼100 meV at a displacement field of 0.9 V nm−1.
259 citations
TL;DR: In this paper, single crystals of phase pure SnS2 were synthesized and analyzed with modern spectroscopic techniques to ascertain the values of relevant semiconductor properties, including electron affinity of 4.16 eV and ionisation potential of 6.44 eV.
Abstract: Tin disulfide is attractive as a potential visible-light photocatalyst because its elemental components are cheap, abundant and environmentally benign. As a 2-dimensional semiconductor, SnS2 can undergo exfoliation to form atomic layer sheets that provide high surface areas of photoactive material. In order to facilitate the deployment of this exciting material in industrial processes and electrolytic cells, single crystals of phase pure SnS2 are synthesised and analysed with modern spectroscopic techniques to ascertain the values of relevant semiconductor properties. An electron affinity of 4.16 eV, ionisation potential of 6.44 eV and work function of 4.81 eV are found. The temperature dependent band gap is also reported for this material for the first time. We confirm the valence band is formed predominately by a mixture S 3p and Sn 5s, while the conduction band consists of a mixture of Sn 5s and 5p orbitals and comment on the agreement between experiment and theory for values of band gaps.
TL;DR: It is found that for homogeneous excitation throughout the crystal, the charge carrier lifetime exceeds 15 μs, which means that the diffusion length in CH3NH3PbI3 can be as large as 50 μm if it is no longer limited by the dimensions of the crystallites.
Abstract: The charge carrier lifetime in organic–inorganic perovskites is one of the most important parameters for modeling and design of solar cells and other types of devices. In this work, we use CH3NH3PbI3 single crystal as a model system to study optical absorption, charge carrier generation, and recombination lifetimes. We show that commonly applied photoluminescence lifetime measurements may dramatically underestimate the intrinsic carrier lifetime in CH3NH3PbI3, which could be due to severe charge recombination at the crystal surface and/or fast electron–hole recombination close to the surface. By using the time-resolved microwave conductivity technique, we investigated the lifetime of free mobile charges inside the crystals. Most importantly, we find that for homogeneous excitation throughout the crystal, the charge carrier lifetime exceeds 15 μs. This means that the diffusion length in CH3NH3PbI3 can be as large as 50 μm if it is no longer limited by the dimensions of the crystallites.
Journal Article•
TL;DR: This work detail a reproducible method for chemical vapor deposition of monolayer, single-crystal flakes of 1T'-MoTe2 and its implementation in next-generation nanoelectronic devices.
Abstract: Growth of transition metal dichalcogenide (TMD) monolayers is of interest due to their unique electrical and optical properties. Films in the 2H and 1T phases have been widely studied but monolayers of some 1T′-TMDs are predicted to be large-gap quantum spin Hall insulators, suitable for innovative transistor structures that can be switched via a topological phase transition rather than conventional carrier depletion [Qian et al. Science 2014, 346, 1344−1347]. Here we detail a reproducible method for chemical vapor deposition of monolayer, single-crystal flakes of 1T′-MoTe2. Atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy confirm the composition and structure of MoTe2 flakes. Variable temperature magnetotransport shows weak antilocalization at low temperatures, an effect seen in topological insulators and evidence of strong spin–orbit coupling. Our approach provides a pathway to systematic investigation of monolayer, single-crystal 1T′-Mo...
TL;DR: The crystal structure of a new bismuth-based light-absorbing material for the application in solar cells was determined by single crystal X-ray diffraction for the first time.
TL;DR: This study strongly suggests that the HfO2-based materials are promising for various ferroelectric applications because of their comparable ferro electric properties including polarization and Curie temperature to conventional ferroElectric materials together with the reported excellent scalability in thickness and compatibility with practical manufacturing processes.
Abstract: Ferroelectricity and Curie temperature are demonstrated for epitaxial Y-doped HfO2 film grown on (110) yttrium oxide-stabilized zirconium oxide (YSZ) single crystal using Sn-doped In2O3 (ITO) as bottom electrodes. The XRD measurements for epitaxial film enabled us to investigate its detailed crystal structure including orientations of the film. The ferroelectricity was confirmed by electric displacement filed – electric filed hysteresis measurement, which revealed saturated polarization of 16 μC/cm2. Estimated spontaneous polarization based on the obtained saturation polarization and the crystal structure analysis was 45 μC/cm2. This value is the first experimental estimations of the spontaneous polarization and is in good agreement with the theoretical value from first principle calculation. Curie temperature was also estimated to be about 450 °C. This study strongly suggests that the HfO2-based materials are promising for various ferroelectric applications because of their comparable ferroelectric properties including polarization and Curie temperature to conventional ferroelectric materials together with the reported excellent scalability in thickness and compatibility with practical manufacturing processes.
TL;DR: In this paper, the authors performed first-principle calculations to investigate the mechanical properties of the monolayer borophene, including ideal tensile strength and critical strain.
Abstract: Very recently, two-dimensional (2D) boron sheets (borophene) with rectangular structures were grown successfully on single crystal Ag(111) substrates (Mannix et al 2015 Science 350 1513). The fabricated boroprene is predicted to have unusual mechanical properties. We performed first-principle calculations to investigate the mechanical properties of the monolayer borophene, including ideal tensile strength and critical strain. It was found that monolayer borophene can withstand stress up to 20.26 N m−1 and 12.98 N m−1 in a and b directions, respectively. However, its critical strain was found to be small. In the a direction, the critical value is only 8%, which, to the best of our knowledge, is the lowest among all studied 2D materials. Our numerical results show that the tensile strain applied in the b direction enhances the bucking height of borophene resulting in an out-of-plane negative Poisson's ratio, which makes the boron sheet show superior mechanical flexibility along the b direction. The failure mechanism and phonon instability of monolayer borophene were also explored.
TL;DR: The improvement in the crystalline quality, together with the rapid growth rate and excellent carrier transport property, provides state-of-the-art single crystalline hybrid perovskite materials for high-performance optoelectronic devices.
Abstract: Single crystal reflects the intrinsic physical properties of a material, and single crystals with high-crystalline quality are highly desired for the acquisition of high-performance devices. We found that large single crystals of perovskite CH3NH3PbI3(Cl) could be grown rapidly from chlorine-containing solutions. Within 5 days, CH3NH3PbI3(Cl) single crystal as large as 20 mm × 18 mm × 6 mm was harvested. As a most important index to evaluate the crystalline quality, the full width at half-maximum (fwhm) in the high-resolution X-ray rocking curve (HR-XRC) of as-grown CH3NH3PbI3(Cl) single crystal was measured as 20 arcsec, which is far superior to so far reported CH3NH3PbI3 single crystals (∼1338 arcsec). The unparalleled crystalline quality delivered a low trap-state density of down to 7.6 × 108 cm–3, high carrier mobility of 167 ± 35 cm2 V–1 s–1, and long transient photovoltaic carrier lifetime of 449 ± 76 μs. The improvement in the crystalline quality, together with the rapid growth rate and excellent c...
TL;DR: M-4-B showed a novel sequential tricolor switching from dark blue to bluish-green and to a reddish color upon grinding, and the boron atom played a key role in developing the single crystal.
Abstract: The single crystal of M-4-B was obtained by attaching the boron of BH3 to the amine linker between a tetraphenylethylene (TPE) unit and rhodamine B. M-4-B showed a novel sequential tricolor switching from dark blue to bluish-green and to a reddish color upon grinding. The boron atom played a key role in developing the single crystal.
TL;DR: The density of trap states within the bandgap of methylammonium lead iodide single crystals is investigated and a comprehensive electronic characterization of crystals is carried out, including measurements of the electron and hole mobility and the energy landscape at the surface.
Abstract: The density of trap states within the bandgap of methylammonium lead iodide single crystals is investigated. Defect states close to both the conduction and valence bands are probed. Additionally, a comprehensive electronic characterization of crystals is carried out, including measurements of the electron and hole mobility, and the energy landscape (band diagram) at the surface.
TL;DR: An elastic organic crystal of a π-conjugated molecule has been fabricated and it was found to be a remarkably elastic crystalline material.
Abstract: An elastic organic crystal of a π-conjugated molecule has been fabricated. A large fluorescent single crystal of 1,4-bis[2-(4-methylthienyl)]-2,3,5,6-tetrafluorobenzene (over 1 cm long) exhibited a fibril lamella morphology based on slip-stacked molecular wires, and it was found to be a remarkably elastic crystalline material. The straight crystal was capable of bending more than 180° under applied stress and then quickly reverted to its original shape upon relaxation. In addition, the fluorescence quantum yield of the crystal was about twice that of the compound in THF solution. Mechanical bending-relaxation resulted in reversible change of the morphology and fluorescence. This research offers a more general approach to flexible crystals as a promising new family of organic semiconducting materials.
TL;DR: The photoluminescence temperature dependence suggested dominance of delayed exciton emission at elevated temperatures, originating from detrapping of carriers from shallow traps or/and from retrapped of electron-hole pairs into exciton states.
Abstract: A thorough investigation of exciton properties in bulk CH3NH3PbBr3 perovskite single crystals was carried out by recording the reflectance, steady-state and transient photoluminescence spectra of submicron volumes across the crystal. The study included an examination of the spectra profiles at various temperatures and laser excitation fluencies. The results resolved the first and second hydrogen-like Wannier–Mott exciton transitions at low temperatures, from which the ground-state exciton’s binding energy of 15.33 meV and Bohr radius of ∼4.38 nm were derived. Furthermore, the photoluminescence temperature dependence suggested dominance of delayed exciton emission at elevated temperatures, originating from detrapping of carriers from shallow traps or/and from retrapping of electron–hole pairs into exciton states. The study revealed knowledge about several currently controversial issues that have an impact on functionality of perovskite materials in optoelectronic devices.
TL;DR: The successful synthesis of the large box-shaped Ag67 NC facilitated by the combined use of phosphine and thiol paves the way for synthesizing other metal clusters with unprecedented shapes by judicious choice of thiols and phosphines.
Abstract: Engineering the surface ligands of metal nanoparticles is critical in designing unique arrangements of metal atoms. Here, we report the synthesis and total structure determination of a large box-shaped Ag67 nanocluster (NC) protected by a mixed shell of thiolate (2,4-dimethylbenzenethiolate, SPhMe2) and phosphine (triphenylphosphine, PPh3) ligands. Single crystal X-ray diffraction (SCXRD) and electrospray ionization mass spectrometry (ESI-MS) revealed the cluster formula to be [Ag67(SPhMe2)32(PPh3)8]3+. The crystal structure shows an Ag23 metal core covered by a layer of Ag44S32P8 arranged in the shape of a box. The Ag23 core was formed through an unprecedented centered cuboctahedron, i.e., Ag13, unlike the common centered Ag13 icosahedron geometry. Two types of ligand motifs, eight AgS3P and eight bridging thiols, were found to stabilize the whole cluster. The optical spectrum of this NC displayed highly structured multiple absorption peaks. The electronic structure and optical spectrum of Ag67 were comp...
TL;DR: A combination of computational and experimental evidence suggests that the spectral line width is a result of multiple, discrete electronic transitions that couple to vibrations of the nanocrystal lattice.
Abstract: Magic-sized nanoclusters have been implicated as mechanistically relevant intermediates in the synthesis of group III-V quantum dots. Herein we report the single-crystal X-ray diffraction structure of a carboxylate-ligated indium phosphide magic-sized nanocluster at 0.83 A resolution. The structure of this cluster, In37P20(O2CR)51, deviates from that of known crystal phases and possesses a non-stoichiometric, charged core composed of a series of fused 6-membered rings. The cluster is completely passivated by bidentate carboxylate ligands exhibiting predominantly bridging binding modes. The absorption spectrum of the cluster shows an asymmetric line shape that is broader than what would be expected from a homogeneous sample. A combination of computational and experimental evidence suggests that the spectral line width is a result of multiple, discrete electronic transitions that couple to vibrations of the nanocrystal lattice. The product of reaction of this nanocluster with 1 equiv of water has also been ...
TL;DR: In this paper, the integration of thin (down to one unit cell) single crystalline, complex oxide films onto silicon substrates, by epitaxial transfer at room temperature, is reported.
Abstract: Single-crystalline thin films of complex oxides show a rich variety of functional properties such as ferroelectricity, piezoelectricity, ferro and antiferromagnetism and so on that have the potential for completely new electronic applications. Direct synthesis of such oxides on silicon remains challenging because of the fundamental crystal chemistry and mechanical incompatibility of dissimilar interfaces. Here we report integration of thin (down to one unit cell) single crystalline, complex oxide films onto silicon substrates, by epitaxial transfer at room temperature. In a field-effect transistor using a transferred lead zirconate titanate layer as the gate insulator, we demonstrate direct reversible control of the semiconductor channel charge with polarization state. These results represent the realization of long pursued but yet to be demonstrated single-crystal functional oxides on-demand on silicon.
TL;DR: Single-crystal perovskite solar cells with a lateral structure yield an efficiency enhancement 44-fold that of polycrystalline thin films, due to the much longer carrier diffusion length.
Abstract: Single-crystal perovskite solar cells with a lateral structure yield an efficiency enhancement 44-fold that of polycrystalline thin films, due to the much longer carrier diffusion length. A piezoelectric effect observed in perovskite single-crystal and the strain-generated grain-boundaries enable ion migration to form a p-i-n structure.
[...]
TL;DR: The first investigation of a time-resolved pump-probe measurement of the second harmonic generation efficiency is reported, showing that SHG efficiency, if nonzero, is below the limit of detection, strongly indicative of a nonpolar or centrosymmetric structure for this compound.
Abstract: In view of the continued controversy concerning the polar/nonpolar nature of the hybrid perovskite system, CH3NH3PbI3, we report the first investigation of a time-resolved pump–probe measurement of the second harmonic generation efficiency as well as using its more traditional form as a sensitive probe of the absence/presence of the center of inversion in the system both in its excited and ground states, respectively. Our results clearly show that SHG efficiency, if nonzero, is below the limit of detection, strongly indicative of a nonpolar or centrosymmetric structure. Our results on the same samples, based on temperature dependent single crystal X-ray diffraction and P–E loop measurements, are entirely consistent with the above conclusion of a centrosymmetric structure for this compound in all three phases, namely the high temperature cubic phase, the intermediate temperature tetragonal phase and the low temperature orthorhombic phase. It is important to note that all our experimental probes are volume ...
TL;DR: The phase behavior of mixed A-site cation methylammonium (MA)/formamidinium (FA) lead iodide hybrid perovskites FAxMA1−xPbI3 has been investigated using powder and variable temperature single crystal X-ray diffraction, with A site composition determined by 1H solution NMR.
Abstract: The phase behaviour of mixed A-site cation methylammonium (MA)/formamidinium (FA) lead iodide hybrid perovskites FAxMA1−xPbI3 has been investigated using powder and variable temperature single crystal X-ray diffraction, with A site composition determined by 1H solution NMR. At room temperature, the crystal class is cubic across the composition range 0.2 ≤ x ≤ 1 but a tetragonal phase is observed for x = 0 (MAPbI3) and x = 0.1. Cooling cubic FAxMA1−xPbI3, 0.2 ≤ x ≤ 1, phases below room temperature results in a phase change to a larger unit cell with tilted [PbI6] octahedra and the temperature at which this occurs, TC→T, decreases sharply until x = 0.2 (TC→T = 257 K) before steadily increasing to TC→T = 283 K for FA0.9MA0.1PbI3. The lattice parameters and optical band gap of cubic FAxMA1−xPbI3, 0.2 ≤ x ≤ 1 at 298 K have been shown to vary in accordance with Vegard's law, though a larger band gap is observed for the tetragonal phases, 0.0 ≤ x ≤ 0.1.
TL;DR: CzCNDSB with a highly twisted conformation in the solid state is constructed and single crystal measurements prove that it possesses an inside pore with a diameter of 8 Å and further forms a long-range orderly arrayed channel.
TL;DR: Jahn–Teller distortions are observed in Au25(SR)18 by single crystal X-ray crystallography and SQUID magnetometry, DFT theory, and linear optical spectroscopy corroborate the finding.
Abstract: The relationship between oxidation state, structure, and magnetism in many molecules is well described by first-order Jahn–Teller distortions. This relationship is not yet well defined for ligated nanoclusters and nanoparticles, especially the nano-technologically relevant gold-thiolate protected metal clusters. Here we interrogate the relationships between structure, magnetism, and oxidation state for the three stable oxidation states, −1, 0 and +1 of the thiolate protected nanocluster Au25(SR)18. We present the single crystal X-ray structures of the previously undetermined charge state Au25(SR)18+1, as well as a higher quality single crystal structure of the neutral compound Au25(SR)180. Structural data combined with SQUID magnetometry and DFT theory enable a complete description of the optical and magnetic properties of Au25(SR)18 in the three oxidation states. In aggregate the data suggests a first-order Jahn–Teller distortion in this compound. The high quality single crystal X-ray structure enables an analysis of the ligand–ligand and ligand–cluster packing interactions that underlie single-crystal formation in thiolate protected metal clusters.