- Synthetic Variation and Structural Trends in Layered Two-Dimensional Alkylammonium Lead Halide Perovskites
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We report the cooling-induced crystallization of layered two-dimensional (2D) lead halide perovskites with controllable inorganic quantum-well thicknesses (n = 1, 2, 3, and 4), organic-spacer chain lengths (butyl-, pentyl-, and hexylammonium), A-site cations (methylammonium and formamidinium), and halide anions (iodide and bromide). Using single-crystal X-ray diffraction, we refined crystal structures for the iodide family as a function of these compositional parameters and across their temperature-dependent phase transitions. In general, lower-symmetry crystal structures, increasing extents of organic-spacer interdigitation, and increasing organic-spacer corrugation tilts are observed at low temperature. Moreover, greater structural distortions are observed in lead halide octahedra closest to the organic-spacer layer, and higher-n structures exhibit periodic variation in Pb-I bond lengths. These structural trends are used to explain corresponding temperature-dependent changes in the photoluminescence spectra. We also provide detailed guidance regarding the combination of synthetic parameters needed to achieve phase-pure crystals of each composition and discuss difficulties encountered when trying to synthesize particular members of the 2D perovskite family containing formamidinium or cesium as the A-site cation. These results provide a foundation for understanding structural trends in 2D lead halide perovskites and the effects these trends have on their thermal, electronic, and optical properties.
- Paritmongkol, Watcharaphol,Dahod, Nabeel S.,Stollmann, Alexia,Mao, Nannan,Settens, Charles,Zheng, Shao-Liang,Tisdale, William A.
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- Controllable perovskite crystallization at a gas-solid interface for hole conductor-free solar cells with steady power conversion efficiency over 10%
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Depositing a pinhole-free perovskite film is of paramount importance to achieve high performance perovskite solar cells, especially in a heterojunction device format that is free of hole transport material (HTM). Here, we report that high-quality pinhole-free CH3NH3PbI3 perovskite film can be controllably deposited via a facile low-temperature (3NH3PbI3·DMF and CH3NH3PbI3·H2O) have been recognized as the main cause for the incomplete coverage of the resultant film. By avoiding these intermediates, the films crystallized at the gas-solid interface offer several beneficial features for device performance including high surface coverage, small surface roughness, as well as controllable grain size. Highly efficient HTM-free perovskite solar cells were constructed with these pinhole-free CH3NH3PbI3 films, exhibiting significant enhancement of the light harvesting in the long wavelength regime with respect to the conventional solution processed one. Overall, the gas-solid method yields devices with an impressive power conversion efficiency of 10.6% with high reproducibility displaying a negligible deviation of 0.1% for a total of 30 cells.
- Hao, Feng,Stoumpos, Constantinos C.,Liu, Zhao,Chang, Robert P. H.,Kanatzidis, Mercouri G.
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- Chemical and Size Characterization of Layered Lead Iodide Quantum Dots via Optical Spectroscopy and Atomic Force Microscopy
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Lead iodide (PbI2) clusters were synthesized from the chemical reaction of NaI (or KI) with Pb(NO3)2 in H2O, D2O, CH3OH, and C3H7OH solvents.The observation of absorption features between the 550 and 350 nm region obtained with an integrating sphere stron
- Mu, R.,Tung, Y. S.,Ueda, A.,Henderson, D. O.
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- Crystal structure of the high-temperature polymorph of C(NH2)3PbI3 and its thermal decomposition
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The synthesis of guanidinium lead iodide, C(NH2)3PbI3 (GUAPbI3), was conducted by slow evaporation of the mixture obtained by dissolving PbI2 and C(NH2)3I in acetonitrile. When the evaporation is done at 40 oC, a yellow needle-like crystals are being formed. The sample was characterized by elemental analysis, density measurements, scanning electron microscopy, thermal analyses, high-temperature X-ray powder diffraction and infrared spectroscopy measurements. The elemental analysis of the obtained crystals confirmed the proposed stoichiometry. The performed thermal analyses showed an endothermic peak associated with structural transition around 160 oC. On the other hand, the endothermic temperature effects above 300 oC are accompanied with mass loss and were interpreted as compound degradation. The crystal structure of high temperature polymorph between 160 oC and 300 oC was determined using high-temperature powder diffraction data measurements at 280 oC using simulated annealing technique in order to obtain initial structural model. The structure was refined using the Rietveld method. At temperatures higher than 160 oC, C(NH2)3PbI3 crystallizes in hexagonal space group P63mc with unit cell parameter a increasing from 9.269 ? to 9.337 ? between 160 oC and 300 oC and c parameter increasing from 15.211 ? to 15.287 ? in the same temperature range. The structure consists of PbI6 octahedra couples sharing a common face, linked with corners. Guanidinium cations are situated in the channels between Pb2I9 couples in a manner that the plane of the molecule is perpendicular to the c-axis.
- Dimitrovska-Lazova, Sandra,Bukleski, Miha,Tzvetkov, Peter,Aleksovska, Slobotka,Kovacheva, Daniela
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- Spatial-confinement effect on phonons and excitons in PbI2 microcrystallites
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We have measured resonant Raman specta and exciton absorption spectra ofPbI2 microcrystallites embedded in ethylene metacrylic acid (E-MAA) cop olymer at 77 and 2 K, respectively. The microcrystallites are platelike and vary in thickness. In the resonant Raman spectra, a new line is observed in the acoustic-phonon energy region, which is intimately related to the excitonabsorption band in the ultrathin microcrystallite with finite number of layers. The phonon energy as a function of the crystal thickness is explained on the basis of a finite chain model. From this analysis, the relationship between the exciton absorption band and the numberof layers is confirmed. Using this relation, we interpret the dependenc e of the exciton energy on the layer thickness, which has been measured previously. Consequently, the thickness dependence of the exciton energyis well explained by the quantum confinement model of the exciton trans lational motion in the crystallites with more than five layers. In crystallites with thinner layers, however, the exciton energies deviate from the theoretical values.
- Saito, Shingo,Goto, Takenari
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- Role of Gravity in the Formation of Liesegang Patterns
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We report the results obtained in four different kinds of experiments designed to test the effect of gravity on the formation of Liesegang patterns.Both reacting solutions (KI and Pb(NO3)2) were gelled with agarose L.The position of the PbI2 precipitates was determined by image analysis, and the kinetic coefficients km = (Xn+1 - Xn)/Xn and kp = (Xn/A)1/n were obtained at different relative orientations of the gravitational field with respect to the direction of the advance of the precipitation front.We conclude that there is not an apparent influence of the gravitational forces on the kinetics of the pattern formation when it is obtained in gelled media at an agarose concentration of 1percent (w/v).When the experiments were performed with agarose at 0.5percent (w/v) or when one of the reacting solutions was ungelled, our tests show clearly the effect of gravity.
- Garcia-Ruiz, J. M.,Rondon, D.,Garcia-Romero, A.,Otalora, F.
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- Rapid sonochemical preparation of shape-selective lead iodide
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Lead iodide (PbI2) films/crystals with various nano/micro morphologies (e.g., Nanoflake, block and microrod) were rapidly synthesized by taking advantage of a simple sonochemical method. The PbI2 crystals with uniform nanoflake structures could be fabricated directly on lead foils with the irradiation time as short as 36 s via interfacial reaction between lead foils and elemental iodine in ethanol at ambient temperature. It was found experimentally that the morphologies of the resulting thin films/crystals could be well controlled by the adjustment of several parameters including irradiation time, reaction solvents, iodine concentration, ultrasonic power, and reaction temperature. Most importantly, the resultant PbI2 films are stable enough to resist rolling under the drastic ultrasound irradiation in a liquid media. This method is believed to be the fastest way for in situ fabrication of morphology-controlled semiconductor films on various metal substrates for subsequent applications related to the other metal iodide or metal sulfide semiconductor films.
- Huang, Baojun,He, Qin,Fa, Wenjun,Li, Pinjiang,Zhang, Yange,Zheng, Zhi
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- Dye J-aggregate-semiconductor nanocrystal hybrid nanostructures in reverse micelles: An experimental study
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Reverse micelle solutions can be used for the assembly of hybrid nanostructures of the composition dye monomer-Ag2S nanocrystal, dye J-aggregate-CuI nanocrystal, and dye J-aggregate-PbI2 nanocrystal. The assembly is effected by means
- Nikolenko,Brichkin,Razumov
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- A novel water-resistant and thermally stable black lead halide perovskite, phenyl viologen lead iodide C22H18N2(PbI3)2
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A novel black organoammonium iodoplumbate semiconductor, namely phenyl viologen lead iodide C22H18N2(PbI3)2 (PhVPI), was successfully synthesized and characterized. This material showed physical and chemical properties suitable for photovoltaic applications. Indeed, low direct allowed band gap energy (Eg = 1.32 eV) and high thermal stability (up to at least 300 °C) compared to methylammonium lead iodide CH3NH3PbI3 (MAPI, Eg = 1.5 eV) render PhVPI potentially attractive for solar cell fabrication. The compound was extensively characterized by means of X-ray diffraction (performed on both powder and single crystals), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), UV-photoelectron spectroscopy (UPS), FT-IR spectroscopy, TG-DTA, and CHNS analysis. Reactivity towards water was monitored through X-ray powder diffraction carried out after prolonged immersion of the material in water at room temperature. Unlike its methyl ammonium counterpart, PhVPI proved to be unaffected by water exposure. The lack of reactivity towards water is to be attributed to the quaternary nature of the nitrogen atoms of the phenyl viologen units that prevents the formation of acid-base equilibria when in contact with water. On the other hand, PhVPI's thermal stability was evaluated by temperature-controlled powder XRD measurements following an hour-long isothermal treatment at 250 and 300 °C. In both cases no signs of decomposition could be detected. However, the compound melted incongruently at 332 °C producing, upon cooling, a mostly amorphous material. PhVPI was found to be slightly soluble in DMF (～5 mM) and highly soluble in DMSO. Nevertheless, its solubility in DMF can be dramatically increased by adding an equimolar amount of DMSO. Therefore, phenyl viologen lead iodide can be amenable for the fabrication of solar devices by spin coating as actually done for MAPI-based cells. The crystal structure, determined by means of single crystal X-ray diffraction using synchrotron radiation, turned out to be triclinic and consequently differs from the prototypal perovskite structure. In fact, it comprises infinite double chains of corner-sharing PbI6 octahedra along the a-axis direction with phenyl viologen cations positioned between the columns. Finally, the present determination of PhVPI's electronic band structure achieved through UPS and UV-Vis DRS is instrumental in using the material for solar cells.
- Latini, Alessandro,Quaranta, Simone,Menchini, Francesca,Lisi, Nicola,Di Girolamo, Diego,Tarquini, Ombretta,Colapietro, Marcello,Barba, Luisa,Demitri, Nicola,Cassetta, Alberto
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- Predominance of covalency in water-vapor-responsive MMX-type chain complexes revealed by 129I Moessbauer spectroscopy
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129I Moessbauer spectroscopy was applied to water-vapor-responsive MMX-type quasi-one-dimensional iodide-bridged Pt complexes (MMX chains) in order to investigate their electronic state quantitatively. Two sets of octuplets observed in K2(H 3NC3H6NH3)[Pt2(pop) 4I]·4H2O (2·4H2O) and one octuplet observed in K2(cis-H3NCH2CHCHCH 2NH3)[Pt2(pop)4I]·4H 2O (1·4H2O) and dehydrated complexes (1 and 2) indicate a unique alternating charge-polarization + charge-density-wave (ACP + CDW) electronic state and a charge-density-wave (CDW) electronic state, respectively. These spectra correspond to their crystal structure and the change of electronic states upon dehydration. Since these complexes consist of an alternating array of positively charged and negatively charged layers, the charge on the iodide ion (ρIS) was discussed on the basis of the isomer shift (IS). The ρIS of the water-vapor-responsive MMX chains was mainly -0.13 to -0.21, which are the smallest of all MMX chains reported so far. Hence, it indicates that the negative charge on the iodide ion is strongly donated to the Pt ion in these complexes. This covalent interaction predominates in the ACP + CDW state as well as in the CDW state. Therefore, the ACP + CDW state is in fact the CDW state with the ACP-type lattice distortion. Because the ρIS became smaller with the decreasing Pt-I-Pt distance, it can be concluded that the covalent interaction plays an important role in determining the electronic states of the MMX chains with pop (= P 2H2O52-) ligands.
- Iguchi, Hiroaki,Kitao, Shinji,Seto, Makoto,Takaishi, Shinya,Yamashita, Masahiro
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- Reentrant Structural and Optical Properties and Large Positive Thermal Expansion in Perovskite Formamidinium Lead Iodide
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The structure of the hybrid perovskite HC(NH2)2PbI3(formamidinium lead iodide) reflects competing interactions associated with molecular motion, hydrogen bonding tendencies, thermally activated soft octahedral rotations, and the propensity for the Pb2+lone pair to express its stereochemistry. High-resolution synchrotron X-ray powder diffraction reveals a continuous transition from the cubic α-phase (Pm3m, #221) to a tetragonal β-phase (P4/mbm, #127) at around 285 K, followed by a first-order transition to a tetragonal γ-phase (retaining P4/mbm, #127) at 140 K. An unusual reentrant pseudosymmetry in the β-to-γ phase transition is seen that is also reflected in the photoluminescence. Around room temperature, the coefficient of volumetric thermal expansion is among the largest for any extended crystalline solid.
- Fabini, Douglas H.,Stoumpos, Constantinos C.,Laurita, Geneva,Kaltzoglou, Andreas,Kontos, Athanassios G.,Falaras, Polycarpos,Kanatzidis, Mercouri G.,Seshadri, Ram
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- Sonochemical synthesis of nano-sized metal-organic lead(II) polymer: A precursor for the preparation of nano-structured lead(II) iodide and lead(II) oxide
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Nanoparticles of a new PbII metal-organic polymer, [Pb(μ-pyr)(μ-I)2]n (1), with a net-like morphology have been synthesized by the reaction of pyrazine with Pb(NO3)2 and NaI via sonochemical irradiati
- Aslani, Alireza,Morsali, Ali
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- High purity lead iodide for crystal growth and its characterization
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High-purity lead iodide (PbI2) is prepared by precipitation of lead nitrate (Pb(NO3)) and potassium iodide (KI) solutions. Thoroughly dried PbI2 is then zone-refined. The main impurity causing strong adherence of the solidified melt to the glass ampoule wall is identified as lead hydroxyl iodate (Pb(OH)I). In order to decrease the OH- concentration and consequently the deviation from stoichiometry, molten PbI2 is treated with a gaseous mixture of methylene iodide (CH2I2) and iodoethane (C2H5I). The criterion for the efficiency of this scavenging process is the removal of the adhesive effect; thus, the solidified PbI2 ingot can move freely in the ampoule. A wet chemical analytic method for determining the deviations from stoichiometry is described.
- Eckstein, J.,Erler, B.,Benz, K. W.
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- Formation mechanism of freestanding CH3NH3PbI3 functional crystals: In situ transformation vs dissolution-crystallization
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To date, the formation mechanism of organolead halide CH3NH3PbI3 perovskites based on the efficient sequential reaction route has remained virtually unexplored. Such a synthetic method usually yields high-performance solar cells with an efficiency over 15%, and the identification of the crystal growth mechanism is crucial for understanding the chemical reaction process and further improving the light converting efficiency. Herein, we develop a versatile and facile approach based on sequential reaction to produce freestanding CH3NH3PbI3 crystals as a model for crystal growth mechanism studies. It was found that the in situ transformation and dissolution-crystallization mechanisms play competing roles in determining the characteristics of products that are largely depend on the chemical reaction kinetics. Such a method can also be readily used for synthesis of freestanding CH3NH3PbI3 crystals with controllable morphological characteristics, such as cuboids, rods, wires, and plates. The synthetic strategy as well as the crystal growth mechanisms exemplified here can also serve in the design and development of more sophisticated organolead halide perovskites as well as further optimization across a range of possible domains of applications.
- Yang, Shuang,Zheng, Yi Chu,Hou, Yu,Chen, Xiao,Chen, Ying,Wang, Yun,Zhao, Huijun,Yang, Hua Gui
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- Hybrid Perovskites with Larger Organic Cations Reveal Autocatalytic Degradation Kinetics and Increased Stability under Light
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Hybrid organic-inorganic perovskites have shown incredible promise as active materials for photovoltaic devices, but their instability to light remains a significant roadblock in realizing these applications. Changing the organic cation has been shown to affect light-induced degradation. As a strategy for increasing the stability of these materials, we replaced varying percentages of methylammonium ion in the archetypical methylammonium lead iodide (MAPbI3) hybrid organic-inorganic perovskite with three significantly larger organic ammonium cations: imidazolium, dimethylammonium, and guanidinium. We were able to synthesize hybrid organic-inorganic perovskites with the same 3D perovskite structure as MAPbI3 with substitution of the larger ions as high as 20-30%. These substituted hybrid organic-inorganic perovskites retained similar optoelectronic properties. We discovered that the light-induced degradation in MAPbI3 and its substituted derivatives is autocatalytic, and we calculated rate coefficients for the degradation. All of the substituted hybrid organic-inorganic perovskites showed light-induced degradation slower than that of MAPbI3, up to a 62% decrease in degradation rate coefficient, at all substitution percentages up to 20%. This work provides evidence that a high percentage of a variety of large ammonium cations can be substituted into the hybrid organic-inorganic perovskite lattice without compromising its desirable optoelectronic properties. Insight into the autocatalytic mechanism of light-induced degradation will be valuable for designing additional strategies to improve the stability of hybrid organic-inorganic perovskites. We also offer insights into how factors other than size, such as hydrogen bonding, influence the stability of the materials. Overall, we have shown that substitution of methylammonium ion for the much larger imidazolium, dimethylammonium, and guanidinium cations in MAPbI3 is a valid strategy for creating stable hybrid organic-inorganic perovskite derivatives by slowing the rate of light-induced degradation.
- Ellis, Christie L. C.,Javaid, Hamza,Smith, Emily C.,Venkataraman
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- The volatile trimethylplatinum(IV) complexes: Effect of β-diketonate substituents on thermal properties
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The series of trimethylplatinum(IV) complexes with a general formula (CH3)3Pt(L)Py: [L? = β-diketonate ligand: (1) tBuC(O)CHC(O)C(OCH3)(CH3)2) – L1, (2) CF3C(O)CHC(O)CC(CH3)2 (OCH3)) – L2, (3) CF3C(O)CHC(O)C4H3S – ttfa, (4) CF3C(O)CHC(O)tBu – ptac, Py –pyridine] were synthesized with high yields using novel synthesis technique based on the interaction of (CH3)3PtI with an appropriate PbL2. A number of methods including elemental analysis, IR and NMR spectroscopy, were used to identify the purity of complexes. Both 1 and 3 crystals are monoclinic, P21/n, Z = 4. The crystallographic parameters are: a = 9.3199(11)?, b = 16.1798(19)?, c = 14.1544(13)?, β = 90.090(4)°, V = 2134.4(4)?3 for 1; a = 10.5676(3)?, b = 17.1804(5)?, c = 12.0353(4)?, β = 90.7430(10)°, V = 2184.89(11)?3 for 3, respectively. The temperature dependences of saturated vapor pressure of the complexes were measured using Knudsen method giving logP = 17.3–6908/T, ΔT = 326–353 K and logP = 17.7–6793/T, ΔT = 303–333 K, for 1 and 4, respectively. The effect of substituents combination in L on thermal stability of (CH3)3Pt(L)Py vapors was studied using mass spectrometry. The energies of Pt[sbnd]N(Py) bonds of (CH3)3Pt(L)Py calculated using DFT approach were in the ranges of 78.97–92.73 and 73.32–83.09 kJ/mol depending on Py rings orientation.
- Dorovskikh, Svetlana I.,Komarov, Vladislav Yu.,Krisyuk, Vladislav V.,Mirzaeva, Irina V.,Morozova, Natalia B.,Trubin, Sergey V.,Turgambaeva, Asia E.
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- Size quantization of excitons in PbI2 microcrystallites
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PbI2 microcrystallites are embedded into E-MAA copolymer by ion exchange method. Platelet shaped microcrystallites with different thicknesses are prepared for the subsequent heat treatment procedures. In the absorption spectra of these samples,
- Goto,Saito,Tanaka
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- Controlling PbI2Stoichiometry during Synthesis to Improve the Performance of Perovskite Photovoltaics
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Over the past decade, remarkable progress has advanced the field of perovskite solar cells to the forefront of thin film solar technologies. The stoichiometry of the perovskite material is of paramount importance as it determines the optoelectronic properties of the absorber and hence the device performance. However, little published work has focused on the synthesis of fully stoichiometric precursor materials of high purity and at high yield. Here, we report a low-cost, energy-efficient, and solvent-free synthesis of the lead iodide precursor by planetary ball milling. With our synthetic approach, we produce low-oxygen, single or multiple polytypic phase PbI2 with tunable stoichiometry. We determine the stoichiometry and the polytypes present in our synthesized materials and further compare them to commercially available materials, using X-ray diffraction, X-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy. Both the stoichiometric PbI2 we synthesized and a substoichiometric commercially available PbI2 (where the iodide content is below the optimum Pb:I atomic ratio of 1:2) were used to grow methylammonium lead iodide microcrystals (which corrects the iodide content). Perovskite solar cells were then produced using stoichiometric and substoichiometric PbI2 mixed with an equimolar amount of methylammonium iodide and compared to devices produced from re-dissolved microcrystals. The photoactive perovskite layer deposition was processed in air, enabled by the use of a single low-toxicity solvent (dimethyl sulfoxide) combined with vacuum-assisted solvent evaporation. We find that the device performance is strongly dependent upon the stoichiometry of the lead iodide precursor, reaching champion efficiencies over 17%, with no obvious correlation with its polytypic phases. This work highlights the critical role of PbI2 stoichiometry in hybrid perovskites as well as demonstrating synthesis methods and perovskite layer fabrication protocols suitable for low-cost solar energy harvesting.
- Tsevas, Konstantinos,Smith, Joel A.,Kumar, Vikas,Rodenburg, Cornelia,Fakis, Mihalis,Mohd Yusoff, Abd. Rashid Bin,Vasilopoulou, Maria,Lidzey, David G.,Nazeeruddin, Mohammad K.,Dunbar, Alan D. F.
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- Inherent electrochemistry of layered post-transition metal halides: The unexpected effect of potential cycling of PbI2
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The development of two-dimensional nanomaterials has expedited the growth of advanced technological applications. PbI2 is a layered inorganic solid with important and unique properties suitable for applications in the detection of electromagnetic radiation. While the optical and electrical properties of layered PbI2 have been generally established, its electrochemistry has remained largely unexplored. In this work, we examine the inherent electrochemistry of PbI2 in relation to its morphological and structural properties. A direct comparison between commercially available and solution-grown PbI2 showed high similarity in properties based on characterizations by X-ray photoelectron spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The respective layered PbI2 materials also exhibited similar inherent electrochemistry. Electrochemical potential cycling of PbI2 in phosphate buffer resulted in the dissolution of iodide ions from PbI2 to form complex lead-phosphate-chloride with the oxygen groups of the phosphate ions while retaining the hexagonal structure. In the cas of KCl solution, the formation of PbO2 was observed.
- Chua, Chun Kiang,Sofer, Zdenk,Lim, Chee Shan,Pumera, Martin
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- Hybrid Organic-Inorganic Coordination Complexes as Tunable Optical Response Materials
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Novel lead and bismuth dipyrido complexes have been synthesized and characterized by single-crystal X-ray diffraction, which shows their structures to be directed by highly oriented π-stacking of planar fully conjugated organic ligands. Optical band gaps are influenced by the identity of both the organic and inorganic component. Density functional theory calculations show optical excitation leads to exciton separation between inorganic and organic components. Using UV-vis, photoluminescence, and X-ray photoemission spectroscopies, we have determined the materials' frontier energy levels and show their suitability for photovoltaic device fabrication by use of electron- and hole-transport materials such as TiO2 and spiro-OMeTAD respectively. Such organic/inorganic hybrid materials promise greater electronic tunability than the inflexible methylammonium lead iodide structure through variation of both the metal and organic components.
- Travis, Will,Knapp, Caroline E.,Savory, Christopher N.,Ganose, Alex M.,Kafourou, Panagiota,Song, Xingchi,Sharif, Zainab,Cockcroft, Jeremy K.,Scanlon, David O.,Bronstein, Hugo,Palgrave, Robert G.
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- Solvent-Mediated Crystallization of CH3NH3SnI3 Films for Heterojunction Depleted Perovskite Solar Cells
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Organo-lead halide perovskite solar cells have gained enormous significance and have now achieved power conversion efficiencies of ～20%. However, the potential toxicity of lead in these systems raises environmental concerns for widespread deployment. Here we investigate solvent effects on the crystallization of the lead-free methylammonium tin triiodide (CH3NH3SnI3) perovskite films in a solution growth process. Highly uniform, pinhole-free perovskite films are obtained from a dimethyl sulfoxide (DMSO) solution via a transitional SnI2·3DMSO intermediate phase. This high-quality perovskite film enables the realization of heterojunction depleted solar cells based on mesoporous TiO2 layer but in the absence of any hole-transporting material with an unprecedented photocurrent up to 21 mA cm-2. Charge extraction and transient photovoltage decay measurements reveal high carrier densities in the CH3NH3SnI3 perovskite device which are one order of magnitude larger than CH3NH3PbI3-based devices but with comparable recombination lifetimes in both devices. The relatively high background dark carrier density of the Sn-based perovskite is responsible for the lower photovoltaic efficiency in comparison to the Pb-based analogues. These results provide important progress toward achieving improved perovskite morphology control in realizing solution-processed highly efficient lead-free perovskite solar cells.
- Hao, Feng,Stoumpos, Constantinos C.,Guo, Peijun,Zhou, Nanjia,Marks, Tobin J.,Chang, Robert P. H.,Kanatzidis, Mercouri G.
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- Pressure-dependent polymorphism and band-gap tuning of methylammonium lead iodide perovskite
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We report the pressure-induced crystallographic transitions and optical behavior of MAPbI3 (MA=methylammonium) using in situ synchrotron X-ray diffraction and laser-excited photoluminescence spectroscopy, supported by density functional theory (DFT) calculations using the hybrid functional B3PW91 with spin-orbit coupling. The tetragonal polymorph determined at ambient pressure transforms to a ReO3-type cubic phase at 0.3 GPa. Upon continuous compression to 2.7 GPa this cubic polymorph converts into a putative orthorhombic structure. Beyond 4.7 GPa it separates into crystalline and amorphous fractions. During decompression, this phase-mixed material undergoes distinct restoration pathways depending on the peak pressure. In situ pressure photoluminescence investigation suggests a reduction in band gap with increasing pressure up to ≈0.3 GPa and then an increase in band gap up to a pressure of 2.7 GPa, in excellent agreement with our DFT calculation prediction. Band aid: Through the determination of methylammonium lead iodide perovskite crystallographic transitions under pressure, in situ laser-excited photoluminescence suggests a reduction in band gap in the tetragonal phase on increasing the pressure up to about 0.3 GPa and then an increase in band gap in ReO3-type cubic phase up to a pressure of 2.7 GPa, a result that is supported by DFT calculations.
- Jiang, Shaojie,Fang, Yanan,Li, Ruipeng,Xiao, Hai,Crowley, Jason,Wang, Chenyu,White, Timothy J.,Goddard, William A.,Wang, Zhongwu,Baikie, Tom,Fang, Jiye
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- Reaction products of methylene iodide with tertiary arsines
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The reactions products of tertiary arsines with methylene iodide are (iodomethyl)trialkyl(aryl)-arsonium iodides. Treatment of the latter with lead(II) nitrate in aqueous ethanol solutions gives rise to an exchange reaction to form the corresponding nitra
- Gigauri,Arabuli,Machaidze,Rusiya
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- Facile synthesis of lead iodide nanostructures by microwave irradiation technique and their structural, morphological, photoluminescence and dielectric studies
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Lead iodide (PbI2) nanostructures have been synthesized by co-precipitation, hydrothermal and rapidly by microwave irradiation techniques. SEM analysis indicated the formation of well aligned nanocrystals and nanorods of average diameter between 100 nm and 400 nm. The powder X-ray diffraction and FT-Raman spectroscopic analysis confirms the formation of a 2H-PbI2 polytypic predominantly. These studies also show that there is no extra phase due to impurity in the synthesized nanostructures. The optical energy band gap of nanostructures prepared by co-precipitation, hydrothermal and microwave irradiation techniques were found to be 2.283, 2.493, 2.542 eV and 2.331. 2.350, 2.375 eV calculated from UV-Vis absorption and diffuse reflectance data, respectively, which shows a clear blue shift in the wavelength due to confinement effect. Photoluminescence spectrum was recorded at different excitation wavelengths and shows clear blue shift in the emission peak which is due to the recombination of free excitons with band to band type transition and also may be due to confinement effect. Further the dielectric studies have been performed and a good enhancement in the dielectric constant has been observed due to small size of the fabricated nanostructures in comparison to bulk material.
- Shkir, Mohd.,Yahia,Alfaify,Abutalib,Muhammad, Shabbir
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- Synthesis, Raman spectroscopy and dielectric properties of Ag:Mn co-doped nanostructured PbI2 for solid state radiation detectors
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Microwave-assisted synthesis of pure and Ag: Mn co-doped PbI2 nanostructures have been reported for the first time. The structural and vibrational confirmations were carried out by X-ray diffraction and FT-Raman spectroscopic analysis. Furtherm
- Yahia,Abutalib
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- New differential thermal analysis study of lead halides
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Lead halides (PbCl2, PbBr2 and PbI2) of various sources were examined by the DTA method in order to analyse polymorphism in these compounds. Only one peak corresponding to melting was found in the DTA curves of high-purity
- Rodova,Cihlar,Malkova,Nitsch
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- Stabilization of Organic-Inorganic Perovskite Layers by Partial Substitution of Iodide by Bromide in Methylammonium Lead Iodide
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Thin films of the methylammonium lead halides CH3NH3Pb(I1-xBrx)3 are prepared on fluorine-doped tin oxide substrates and exposed to humid air in the dark and under illumination. To characterize the st
- Ruess, Raffael,Benfer, Felix,B?cher, Felix,Stumpp, Martina,Schlettwein, Derck
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- Formation and structure of the novel heptanuclear lead(II) oxo cluster [Pb7(μ3-O)(μ4-O) (μ3-OMe)4(μ2-I)4] I2: With an unprecedented cage structure
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A novel lead(II) cluster [Pb7(μ3-O)(μ4-O) (μ3-OMe)4(μ2-I)4] I2 (1) has been isolated from the reaction mixture of PbI2 and pyrazine in DMF/MeOH solvent with a reasonable yield (46%). The X-ray crystallography shows that 1 exhibits a novel unprecedented cage structure with centered μ3-O and μ4-O atoms and four different coordination environments of lead atoms. It is the first structurally characterized example of a lead compound containing bridging oxo, methoxide and iodide ligands. Compound 1 crystallizes in the tetragonal space group P421m, a = b = 11.7768(13), c = 9.8606(16) A, Z = 2, V = 1367.6(3) A3. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Shi, Yu-Jun,Xu, Yan,Chen, Xue-Tai,Xue, Ziling,You, Xiao-Zeng
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- Ba2PO4I, Sr2PO4I, and Pb2PO4I - A new structure type and three of its representatives
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The compound Pb2PO4I was synthesized via a solid state reaction under inert conditions. None of the known structure types of other compounds of the type M2(P,V,As,Cr)O4(F,Cl,Br,I) provided a similar pattern. Structure solution was carried out by evaluation of an X-ray diffractogram of polycrystalline powder using the methods simulated annealing and difference Fourier. Pb2PO4I crystallizes in the/space group P21/c with the lattice parameters a = 9.0451(1) ?, b = 8.7593(1) ?, c = 8.5740(1) ?, and β = 111.128(1)° . The isotypic compounds Sr2PO4I and Ba2PO4I were synthesized, too. Their crystallographic structure was refined by Rietveld analysis. The structure of the three compounds is described and discussed.
- Haberkorn, Robert,Bauer, Jessica,Kickelbick, Guido
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- Iodo bridged lead(II) compounds of azoimidazoles: Single crystal X-ray structures of [di-iodo-{1-methyl-2-(p-tolylazo)imidazole}lead(II)]n and {1-methyl-3-benzyl-2-(p-tolylazo)imidazolium}m-{tri-iodoplumbate(II)}m
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PbI2 forms iodo-bridged neutral polymer upon reaction with 1-alkyl-2-(arylazo)imidazoles (RaaiR′). The reaction of PbI2 and dialkyl imidazolium iodides [RaaiR′R″]+I- has synthesized {1,3-dialkyl-2-(arylazo)imida
- Sarker,Jana,Mostafa,Wu,Lu,Sinha
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- Insight on the optoelectronics and enhanced dielectric properties of strontium decorated PbI2 nanosheets for hot carrier solar cell applications
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Dielectric properties determine by electric field distributions play a decisive role in energy harvesting and storage applications. In this context, strontium decorated lead iodide nanosheets (Sr:PbI2) are prepared, and its vibrational and dielectric properties are studied. The bandgap changes are explained by Brustein-Moss effect and renormalization process. Raman spectral studies reveal that introducing Sr atoms into PbI2 lattice enhance the lifetime of LO phonon through bottleneck effect. Subsequently, the dielectric constant (ε′) values of 5 wt% Sr:PbI2 are increased 20% than pure PbI2. The results conclude that the vibrational properties of Sr decorated PbI2 nanosheets are much significant for hot carrier solar cell devices.
- Mariappan, S. Muthu,Shkir, Mohd,Alshahrani,Elangovan,Algarni,AlFaify
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- Survey of temperature, reaction time and ultrasound irradiation power on sonochemical synthesis of two new nanostructured lead(II) coordination supramolecule compounds
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Nanoparticles of two new 0D, lead(II) coordination supramolecular compounds, [Pb(L)2(I)2] (1) and [Pb(L)(L/)(H2O)]·3H2O (2), (L = 1,10-phenanthroline monohydrate, L/ = 2,6-pyridinedicarboxlic acid), have been synthesized by a sonochemical process and characterized by scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), X-ray powder diffraction (XRPD), FT-IR spectroscopy and elemental analyses. The single crystal X-ray data of compounds show that the Pb ion is six coordinated in both 1 and 2. The thermal stability of compound 1 and 2 has been studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The role of temperature, reaction time and ultrasound irradiation power on the size and morphology of the nano-structured compound obtained from 1 and 2, have been investigated. Results indicate that an increase of temperature and sonication power and a decrease in time reaction led to a decrease of particle size. Topological analysis shows that the compound 1 and 2 are new topology for net: 1,4M5-1 and nch, respectively.
- Hayati, Payam,Rezvani, AliReza,Morsali, Ali,Retailleau, Pascal,Centore, Roberto
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- Deposition of lead iodide films on Rh(1 0 0) electrodes from colloidal solutions - The effect of an iodine adlayer
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The growth of PbI2 precipitates on single crystal substrates from colloidal solutions has been investigated with in air scanning tunneling microscopy and synchrotron-based X-ray photoelectron spectroscopy. The PbI2 growth on Rh(1 0 0) results in nano-clusters with lateral dimensions between 30 and 60 ?, consistent with earlier reports. However, the growth of PbI2 on a well-ordered iodinated Rh(1 0 0), denoted as (√2 × √2)R45°-I, leads to atomically smooth PbI2 films having a hexagonal symmetry with lattice constant identical to the bulk value of 4.5 ?. The heteroepitaxy is believed to be effected by the atomic iodine monolayer that helps to accommodate large lattice mismatch between PbI2 and Rh surface with short-range van der Waals interaction.
- Yang, Chia-Huei,Yau, Shueh-Lin,Fan, Liang-Jen,Yang, Yaw-Wen
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- Hole conductivity estimation in lead iodide film through kinetic study of tarnishing reaction
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Hole conductivity values in compact and adherent PbI2 film grown on Pb have been estimated from the isothermal parabolic rate constants through tarnishing study of pure lead in iodine atmosphere following the inverse procedure of Wagner's tarnishing/scaling equation. Iodide films have been grown inside a specially designed iodination reactor. The investigation has been confined to the temperature and iodine pressure ranges of 423-523 K and 0.615-6.578 kPa, respectively. Estimated hole conductivity values have been found to follow a pressure dependence relation of the type σh? = σ0h?p1/2I2 with an associated activation energy value of 66 kJ.mol-1. The iodide film has been characterised by SEM, EDS and XRD analyses.
- Kuiry,Roy,Bose
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- Synthesis, physico-chemical characterization and structure of the elusive hydroxylammonium lead iodide perovskite NH3OHPbI3
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The synthesis of hydroxylammonium lead iodide NH3OHPbI3 was accomplished by means of the reaction between water solutions of HI and NH2OH with PbI2 in sulfolane in conjunction with either crystallization by CH2Cl2 vapor diffusion or sulfolane extraction with toluene. The appropriate choice of the solvent was found to be crucial in order to attain the desired material. The synthesized compound was extensively characterized by single crystal and powder X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, FT-IR spectroscopy, 1H-NMR spectroscopy, TG-DTA-QMS EGA (Evolved Gas Analysis), ESI-MS, and CHNS analysis. NH3OHPbI3 is an extremely reactive, deliquescent solid that easily oxidizes in air releasing iodine. Furthermore, it is the first reported perovskite to melt (m.p. around 80 °C) before decomposing exothermally at 103 °C. Such a chemical behavior, together with its optical absorption properties (i.e. yellow-colored perovskite), renders this material totally unsuitable for photovoltaic applications. The deliquescence of the material is to be ascribed to the strong hydrophilicity of hydroxylammonium ion. On the other hand, the relatively high Br?nsted acidity of hydroxylammonium (pKa = 5.97) compared to other ammonium cations, promotes the reduction of atmospheric oxygen to water and the NH3OHPbI3 oxidation. The crystal structure, determined by single crystal X-ray diffraction with synchrotron radiation, is orthorhombic, but differs from the prototypal perovskite structure. Indeed it comprises infinite chains of face-sharing PbI6 octahedra along the c-axis direction with hydroxylammonium cations positioned between the columns, forming layers on the ac plane. The solvent intercalates easily between the layers. The crystal structure is apparently anomalous considering that the expected Goldschmidt's tolerance factor for the system (0.909) lies in the range of a stable prototypal perovskite structure. Therefore, the strong hydrogen bond forming tendency of hydroxylamine is likely to account for the apparent structural anomaly.
- D'Annibale, Andrea,Panetta, Riccardo,Tarquini, Ombretta,Colapietro, Marcello,Quaranta, Simone,Cassetta, Alberto,Barba, Luisa,Chita, Giuseppe,Latini, Alessandro
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- Synthesis, properties, and theoretical studies of new stepwise layered lodoplumbate: [ni(opd)2(acn)2]n[pb 4i10]n
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A novel 2D layered iodoplumbate, [Ni(opd)2(acn) 2]n[Pb4l10]n (1), yellow-green in color, has been synthesized. The anionic [Pb4l 102-]n layer is
- Li, Jin-Peng,Li, Long-Hua,Wu, Li-Ming,Chen, Ling
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- Pronounced effect of PbI2 nanoparticles doping on optoelectronic properties of PVA films for photo-electronic applications
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Composite films of polyvinyl alcohol/lead iodide (PVA/PbI2) were prepared with different concentrations of PbI2 using low-cost casting process. The characteristics of the prepared films were analyzed by XRD and SEM. The XRD results s
- Ashraf, I. M.,El-Zahhar, Adel A.,Idris, Abubakr M.,Zkria, Abdelrahman
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- Fabrication of stable and efficient 2D/3D perovskite solar cells through post-treatment with TBABF4
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Perovskite solar cells (PSCs), with their low cost and simple fabrication, have emerged as promising devices to solve global warming issues. In this study, tetrabutylammonium tetrafluoroborate (TBABF4) was used as a passivator to boost the performance and the stability of the fabricated PSCs. Through TBABF4post-treatment, the perovskite film's grain boundaries were passivated, which caused a reduction of charge traps on the surface of the perovskite layer and served as interfacial engineering at the perovskite/hole transport layer (HTL) interface. It was found that TBABF4can act as a source of TBA+cations and cause the formation of a 2D/3D heterostructure layer, which increases the stability of PSCs. Indeed, the 2D/3D structure derived from TBABF4solution plays the role of a shield layer to protect the surface of the perovskite layer from degradation and facilitates charge transport processes. The post-treatment of perovskite films is, thus, introduced as an approach to address both the stability and the performance of PSCs and as a step forward to commercialize PSCs.
- Dehghanipour,Behjat,Amrollahi Bioki
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supporting information
p. 957 - 966
(2021/02/06)
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- Influence of halide mixing on thermal and photochemical stability of hybrid perovskites: XPS studies
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The effect of I–/Cl–and I–/Br–mixing on the thermal and photochemical degradation of organometallic perovskite MeNH3PbI3 (MAPbI3) was studied by X-ray photoelectron spectroscopy, which revealed the opportunity to essentially increase the photo and thermal stabilities of the material depending on the level and position of halide-mixing. The largest positive effect was observed for the small concentration of chloride substituent (MAPbI2.7Cl0.3), while the full halide substitution (MAPbBr3) had a negative effect on the stability of hybrid perovskite.
- Zhidkov, Ivan S.,Akbulatov, Azat F.,Kukharenko, Andrey I.,Cholakh, Seif O.,Stevenson, Keith J.,Troshinb, Pavel A.,Kurmaev, Ernst Z.
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p. 381 - 383
(2018/08/10)
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- Formation of high-quality perovskite thin film for planar heterojunction solar cells
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Constructing uniform, flat perovskite thin films is of paramount essence to achieve high performance and reproducible perovskite photovoltaic devices. However, the sequential deposition technique, which usually shows efficiencies over 17%, still failed to enable the formation of uniform, pinhole-free films by solution processing, whereas such high-quality films can be prepared within the vapor medium. Here we demonstrate that such high-quality film can also be realized upon a solution process via judicious choice of solvents, particularly by controlling of lead dissolution phenomenon. We found that alcohol solvents with appropriate molecular structures such as tert-butanol, can facilitate the in situ intercalation of ammonium cations into PbI2 matrix, and thus give flat mirror-like tetragonal perovskite film with resemble surface roughness to that from vapor assisted method. Planar heterojunction solar cells constructed with these solution-processed thin films yielded a high power conversion efficiency of 14.61%, extremely higher than that of conventional method under standard one sun conditions. This solvent-mediated strategy provides a new approach towards the goal of high-performance, low-cost and reproducible devices with simple solution processes.
- Yang, Shuang,Chen, Ying,Zheng, Yi Chu,Chen, Xiao,Hou, Yu,Yang, Hua Gui
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p. 69502 - 69508
(2015/09/01)
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- Chemical Pathways Connecting Lead(II) Iodide and Perovskite via Polymeric Plumbate(II) Fiber
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Despite tremendous progress in optoelectronic devices using lead perovskite (CH3NH3+PbI3-), there has been a paucity of mechanistic information on how photoactive micron-sized crystals of lead perovskite grow from a mixture of a layered crystal of lead(II) iodide and methylammonium iodide mediated by a polar solvent, DMSO or DMF. We report here that the whole process of the lead perovskite synthesis consists of a series of equilibria driven by reversible solvent participation involving a polymeric strip of plumbate(II) oligomer as a key intermediate. A significant finding includes quick decomposition of perovskite crystal upon exposure to DMSO or DMF at room temperature, where the solvent molecules act as a base to remove acidic ammonium iodide from the perovskite crystal. This observation accounts for the difficulty in controlling perovskite solar cell fabrication. Overall, the polar solvent is indispensible first to degrade a 2-D sheet of crystals of lead(II) iodide into 1-D fibrous intermediates and then to promote Oswald ripening of perovskite crystals. The detailed chemical information provided here will help to rationalize the photovoltaic device studies that have so far remained empirical and to open a new venue to a developing field of microscale lead perovskite devices, as illustrated by fabrication of photovoltaic devices and photodetectors.
- Guo, Yunlong,Shoyama, Kazutaka,Sato, Wataru,Matsuo, Yutaka,Inoue, Kento,Harano, Koji,Liu, Chao,Tanaka, Hideyuki,Nakamura, Eiichi
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p. 15907 - 15914
(2016/01/09)
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- Pseudohalide-Induced Moisture Tolerance in Perovskite CH3NH3Pb(SCN)2I Thin Films
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Two pseudohalide thiocyanate ions (SCN-) have been used to replace two iodides in CH3NH3PbI3, and the resulting perovskite material was used as the active material in solar cells. In accelerated stability tests, the CH3NH3Pb(SCN)2I perovskite films were shown to be superior to the conventional CH3NH3PbI3 films as no significant degradation was observed after the film had been exposed to air with a relative humidity of 95% for over four hours, whereas CH3NH3PbI3 films degraded in less than 1.5 hours. Solar cells based on CH3NH3Pb(SCN)2I thin films exhibited an efficiency of 8.3%, which is comparable to that of CH3NH3PbI3 based cells fabricated in the same way.
- Jiang, Qinglong,Rebollar, Dominic,Gong, Jue,Piacentino, Elettra L.,Zheng, Chong,Xu, Tao
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p. 7617 - 7620
(2015/06/25)
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- Semiconducting tin and lead iodide perovskites with organic cations: Phase transitions, high mobilities, and near-infrared photoluminescent properties
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A broad organic-inorganic series of hybrid metal iodide perovskites with the general formulation AMI3, where A is the methylammonium (CH 3NH3+) or formamidinium (HC(NH 2)2+) cation and M is Sn (1 and 2) or Pb (3 and 4) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X-ray diffraction analysis of 1-4 classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature-dependent single crystal X-ray diffraction in the 100-400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temperature-dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that 1-4 behave as direct-gap semiconductors with energy band gaps distributed in the range of 1.25-1.75 eV. The compounds exhibit an intense near-IR photoluminescence (PL) emission in the 700-1000 nm range (1.1-1.7 eV) at room temperature. We show that solid solutions between the Sn and Pb compounds are readily accessible throughout the composition range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled as we show for the isostructural series of solid solutions CH3NH3Sn1-xPbxI 3 (5). The charge transport type in these materials was characterized by Seebeck coefficient and Hall-effect measurements. The compounds behave as p- or n-type semiconductors depending on the preparation method. The samples with the lowest carrier concentration are prepared from solution and are n-type; p-type samples can be obtained through solid state reactions exposed in air in a controllable manner. In the case of Sn compounds, there is a facile tendency toward oxidation which causes the materials to be doped with Sn4+ and thus behave as p-type semiconductors displaying metal-like conductivity. The compounds appear to possess very high estimated electron and hole mobilities that exceed 2000 cm2/(V s) and 300 cm2/(V s), respectively, as shown in the case of CH3NH3SnI 3 (1). We also compare the properties of the title hybrid materials with those of the all-inorganic CsSnI3 and CsPbI 3 prepared using identical synthetic methods.
- Stoumpos, Constantinos C.,Malliakas, Christos D.,Kanatzidis, Mercouri G.
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supporting information
p. 9019 - 9038
(2013/09/02)
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- Sonochemical syntheses of nano lead(II) iodide triazole carboxylate coordination polymer: Precursor for facile fabrication of lead(II) oxide/iodide nano-structures
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Nanoparticles of a one-dimensional coordination polymer [Pb(L)(μ2-I)]n (1), (L- = 1H-1,2,4-triazole-3-carboxylate), have been synthesized by a sonochemical process and characterized by field emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRPD), FT-IR spectroscopy and elemental analyses. The thermal stability of compound 1 both its bulk and nano-size has been studied by thermal gravimetric (TG) and compared each other. Concentration of initial reagents effects and the role of power ultrasound irradiation on size and morphology of nano-structured compound 1 have been studied and show that low concentrations of initial reagents and also high power of ultrasound irradiation decreased particles size and leaded to uniform nanoparticles morphology. PbO nano-structures were simply synthesized by solid-state transformation of compound 1 at 630 °C under air atmosphere whereas thermal decomposition of compound 1 in oleic acid as surfactant at 200 °C yield PbI2 nanoparticles.
- Safarifard, Vahid,Morsali, Ali
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p. 151 - 157
(2013/05/22)
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- Research on phase transition and crystal growth of lead iodide
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Based on Pb-I phase diagram, phase transition of PbI2 immiscible melt (L2 + L3) was analyzed. It indicates that PbI 2 crystal growth is accompanied with precipitation of excessive Pb. Hereby, with an improved gr
- Zhu, Xing-Hua,Zhang, Hai-Bo,Yang, Ding-Yu,Wei, Zhao-Rong,Gao, Xiu-Ying,Yang, Jun
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- Synthesis and structural characterisation of the lead-platinum sulfido aggregates [Pt2(μ-S)2(PPh3)4PbX2] (X = Br, I); promotion of rare tetrahedral geometry for lead(II)
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The reactions of [Pt2(μ-S)2(PPh3)4] with excess PbBr2 or PbI2 in methanolic suspension result in the formation of the neutral lead(II) halide adducts [Pt2(μ-S)2(PPh3)4PbX2] (X = Br, I). The X-ray structure determination of the lead iodide adduct reveals an essentially tetrahedral lead(II) centre, which is a rare coordination geometry for lead(II), which almost invariably is hemidirected, with a stereochemically active lone pair. In contrast, the structure of the PbBr2 adduct, although suffering from some disorder, shows a more typical, distorted arrangement of ligands; these results are discussed in terms of the tendency for soft, bulky ligands to promote symmetric, holodirected geometries. The ESI mass spectra of the adducts are reported, and yield [M-halide]+ ions.
- Henderson, William,Hor, T.S. Andy
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p. 1859 - 1863
(2010/09/04)
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- Carbon dioxide activation by "Non-nucleophilic" lead alkoxides
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A series of terminal lead alkoxides have been synthesized utilizing the bulky β-diketiminate ligand [{N(2,6-iPr2C 6H3)-C(Me)}2CH]- (BDI). The nucleophilicities of these alkoxides have been examined, and unexpected trends were observed. For instance, (BDI)PbOR reacts with methyl iodide only under forcing conditions yet reacts readily, but reversibly, with carbon dioxide. The degree of reversibility is strongly dependent upon minor changes in the R group. For instance, when R = isopropyl, the reversibility is only observed when the resulting alkyl carbonate is treated with other heterocumulenes; however, when R = tert-butyl, the reversibility is apparent upon any application of reduced pressure to the corresponding alkyl carbonate. The differences in the reversibility of carbon dioxide insertion are attributed to the ground-state energy differences of lead alkoxides. The mechanism of carbon dioxide insertion is discussed.
- Tam, Eric C.Y.,Johnstone, Nick C.,Ferro, Lorenzo,Hitchcock, Peter B.,Fulton, J. Robin
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p. 8971 - 8976
(2009/12/25)
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- A model of the formation of liesegang rings under stimulated precipitation conditions
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A mathematical apparatus for describing the kinetics of chemical reactions accompanied by phase transitions is suggested. The phenomenon of stimulated precipitation is singled out. Together with spontaneous precipitation-solution, it allows periodic sedimentation (Liesegang rings) to be correctly described and the concept of solubility product to be corrected and generalized. Pleiades Publishing, Inc., 2006.
- Skorobogatov,Kamenskii
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p. 714 - 725
(2007/10/03)
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- Stable and metastable phases in reciprocal systems PbSe + Ag 2I2 = Ag2Se + PbI2 and PbSe + CdI2 = CdSe + PbI2
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Reciprocal system PbSe + Ag2I2 = Ag2Se + PbI2 was studied. Diagonal Ag2Se-PbI2 is stable. The liquidus surface and an isothermal section at 633 K for the PbSe-Ag2Se-PbI2 system (stable equilibria) were designed. Transformations leading to the crystallization of a metastable ternary compound in the PbSe-PbI2 system and metastable lead iodide polytypes in the PbSe-Ag2Se-PbI2 system in the range 620-685 K were studied. Quenching from melt (1150-1220 K) yielded new intermediate metastable phases that crystallize in the CdCl2 structural type in the PbSe-Ag2Se-PbI2 and PbSe + CdI2 = CdSe + PbI2 systems. Copyright
- Odin,Grin'ko,Kozlovskii,Safronov
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p. 767 - 771
(2008/10/09)
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- Formation of stable and metastable phases in reciprocal systems PbSe + MI2 = MSe + PbI2 (M = Hg, Mn, Sn)
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The reciprocal system PbSe + HgI2 = HgSe + PbI2 has been investigated. It has been shown that the HgSe-PbI2 diagonal is stable. The liquidus surface and an isothermal section at 633 K of the phase diagram of the PbSe-HgSe-PbI2 system (stable equilibria) have been designed. Transformations that lead to the crystallization of a metastable ternary compound in the PbSe-PbI2 system and the metastable polytypes of lead iodide in reciprocal systems PbSe + HgI2 = HgSe + PbI 2 and PbSe + MnI2 = MnSe + PbI2 in the temperature range 620-685 K have been investigated. New intermediate metastable phases in the systems PbSe + MI2 = MSe + PbI2 (M = Hg, Mn, Sn), which crystallize in the CdCl2 structural type, have been obtained by melt quenching, and their unit cell parameters are determined.
- Odin,Grin'ko,Kozlovskii,Safronov,Gapanovich
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p. 1444 - 1449
(2008/10/09)
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- Intercalation and formation of complexes in the system of lead(II) iodide-ammonia
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Interaction between lead(II) iodide and ammonia was studied with the help of an X-ray in situ analysis, DTA-TG analysis, DSC measurements and IR spectroscopy. A two-stage mechanism of the reaction was defined. At the first stage of the reaction two phases with trigonal symmetry and a phase with monoclinic symmetry are developed. At the second stage of the reaction the structure changes lead to formation of a compound with orthorhombic symmetry. The results were discussed along with the data of thermal analysis and IR spectroscopy. The value of enthalpy of formation for the compound PbI 2(NH3)4 was determined.
- Gurina,Savchenko
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p. 909 - 915
(2008/10/09)
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- Effect of growth conditions on the morphology and structural perfection of vapor-grown PbI2 crystals
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Data are presented on the morphology and structural perfection of PbI 2 crystals grown from the vapor phase in a closed system. By varying growth conditions, platelike, ribbon, needle, twinned, and dendritic crystals were prepared, as well as combinations and intergrowths of these habits.
- Kurilo,Rybak
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p. 288 - 291
(2008/10/08)
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- Diffusion kinetics of spatial distribution formation for liquid-phase reaction products
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The kinetics of the formation of the spatial structure of product precipitation zones in the Pb(NO3)2 + K2CrO4, Pb(NO3)2 + KI, CoCl2 + KOH, and CoCl2, CuCl2 + KOH reactions under the conditions of diffusion counterflows of the reagents in aqueous gels was studied. The dependence of the spatial distribution of reaction products on reagent concentrations and reaction conditions was analyzed. The critical product concentrations in the precipitation region were determined. The experimental results were compared with the theoretical predictions based on the supersaturation model.
- Gorshenev,Ershov
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p. S476-S482
(2007/10/03)
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- Unsealed Ultrasound-Assisted Synthesis of Cadmium and Lead Iodide Intercalation Compounds
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The ultrasonic effect on the interaction and phase composition of compounds of cadmium and lead iodides with organic cyclic amines such as pyridine (py), piperidine (pp), and aniline (an) was studied. The samples were characterized by thermal and X-ray powder diffraction analyses; their NQR and IR spectra were recorded. Novel, ultimately, intercalated phases were prepared: PbI2pp8.3 ± 0.2, CdI2py4.3 ± 0.2, and CdI2py6.0 ± 0.2. The ultrasonic treatment significantly shortened the equilibration time in the systems in question. Complex formation proved to be more profitable in terms of energy for the CdI2-py, CdI2-an, and CdI2-pp systems.
- Konopleva,Venskovskii,Tupoleva,Babushkina
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p. 1164 - 1167
(2008/10/08)
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- Estimation of ionic conductivity of lead iodide film through tarnishing study
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Ionic conductivity values as a function of temperature and iodine pressure in compact and adherent PbI2 film grown on pure Pb have been estimated from the isothermal parabolic rate constants through tarnishing study under short-circuit condition. Iodide films have been grown inside a specially designed iodination reactor in the temperature and iodine pressure ranges of 423-523 K and 0.615-6.578 kPa, respectively. Estimated ionic conductivity values have been found to follow a pressure dependence relation of the type σi = σi0 × PI(2)1/3 associated with an activation energy value of 51 kJ·mol-1. The iodide film has been characterized by SEM and EPMA analyses.
- Kuiry,Roy,Bose
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p. 1643 - 1650
(2008/10/08)
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- Structure formation during precipitation reaction in gels new liesegang patterns
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The paper reports on an investigation carried out into one- to three-dimensional Liesegang systems (test tub: arrangement) composed of different concentrations of lead nitrate in Agar gel wilh either potassium iodide or potassium dichromate as the precipitation reagent. A rich variety of different structure formulions, including screw formations of the weakly soluble reaction product is documented. Measurements of the progression of the precipitation front show a dependence of the diffusion path on time that which deviates from the Einstein-Smoiuchowski root mean square displacement. The measured exponent n of the displacement xn=f(t) is discussed in detail and interpreted as the dynamic dimension dw of the diffusion through the fractal medium of the gel, the backhone dimension of which couid be estimated. A cellular automaton model is used to describe the DLA cluster formation of the precipitate as well as the geometrical shape of the Liesegang patterns. WTLEY-VCH Verlag GmbH, 1998.
- Sydow,Plath
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p. 1683 - 1688
(2008/10/08)
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