Search results for "Halide"

Organometal Halide Perovskites: Bulk Low-Dimension Materials and Nanoparticles

2015

Organometal halide perovskites (hybrid perovskites) contain an anionic metal–halogen-semiconducting framework and charge-compensating organic cations. As hybrid materials, they combine useful properties of both organic and inorganic materials, such as plastic mechanical properties and good electronic mobility related to organic and inorganic material, respectively. They are prepared from abundant and low cost starting compounds. The perovskite stoichiometry is associated with the dimensionality of its inorganic framework, which can vary from three to zero, 3D consisting of corner-sharing MX6 octahedra, and 0D consisting of isolated octahedra. Small-sized organic cations can fit into the MX6…

Lattice Opening upon Bulk Reductive Covalent Functionalization of Black Phosphorus

2019

The chemical bulk reductive covalent functionalization of thin-layer black phosphorus (BP) using BP intercalation compounds has been developed. Through effective reductive activation, covalent functionalization of the charged BP by reaction with organic alkyl halides is achieved. Functionalization was extensively demonstrated by means of several spectroscopic techniques and DFT calculations; the products showed higher functionalization degrees than those obtained by neutral routes.

Recombination in Perovskite Solar Cells

2017

Trap-assisted recombination, despite being lower as compared with traditional inorganic solar cells, is still the dominant recombination mechanism in perovskite solar cells (PSCs) and limits their efficiency. We investigate the attributes of the primary trap assisted recombination channels (grain boundaries and interfaces) and their correlation to defect ions in PSCs. We achieve this by using a validated device model to fit the simulations to the experimental data of efficient vacuum-deposited p-i-n and n-i-p CH3NH3PbI3 solar cells, including the light intensity dependence of the open circuit voltage and fill factor. We find that, despite the presence of traps at interfaces and grain bounda…

Raman Imaging of Single Carbon Nanotubes

2000

[19] The single crystals of the Bu4NBr0.6I1.4Cl salt, were obtained by addition of IBr to a solution of Bu4NCl in ethanol at a reagent ratio of 1:0.5. Stoichiometry of the anion has been found by EDX. Based on a Raman study the anion consists of the I2Br ‐ (band at 140 cm ‐1 ), IBr2 ‐ (band at 150‐ 176 cm ‐1 ), BrICl ‐ (band at 225 cm ‐1 ), and ICl2 ‐ (band at 250‐263 cm ‐1 ) trihalide anions. [20] The X-ray diffraction data from single crystals for both trihalide salts were measured using an Enraf Nonius CAD4 diffractometer with graphite monochromatic Mo Ka radiation (k = 0.71073 a) at room temperature. Unit cell parameters of the new a¢¢¢- crystal were determined from a leastsquares analy…

Charge State of Silver Halide Colloids Determines the Antibacterial Activity in Amorphous Calcium Phosphate

2013

Removal of bacteria is important not only at implantation, but after long-term implant/prosthesis use. This requires strategies that employ different approaches for combating bacteria. Halides have the potential of an additional mechanism, and together with silver may provide a more powerful antibacterial strategy. Silver iodide was synthesized as colloids with a positive and negative charge and incorporated into an amorphous calcium phosphate (ACP) to provide a possible greater antibacterial action. Colloids were characterized by FTIR spectroscopy and the charge measured by zeta potential. Phase analysis by X-ray diffraction patterns confirmed the formation of b-AgI nanoparticles. Minimum …

Palladium nanoparticles–polypyrrole composite as an efficient catalyst for cyanation of aryl halides

2014

Abstract New palladium-polypyrrole (Pd/PPy) nanocomposites have been studied in cyanation of aryl halides with K 4 Fe(CN) 6 and showed high catalytic efficiency. Aryl iodides, bromides, and chlorides are active. The reaction can be performed both in organic solvents and in water; in the latter case, the catalyst was immobilized on graphite support. The cyanation of inactivated aryl chlorides is of special importance as only a few publications dealing with efficient cyanation of aryl chlorides are available, in which expensive and poisonous phosphine ligands and non-aqueous solvents are used. The influence of the morphology of the catalyst on its efficiency in cyanation was investigated, and…

The role of surface chemical states on the photocatalytic behavior of all-inorganic mixed halide perovskite nanocrystals

2019

Influence of hole transport material ionization energy on the performance of perovskite solar cells

2019

Halide perovskites have shown excellent photophysical properties for solar cell applications which led to a rapid increase of the device efficiency. Understanding the charge carrier dynamics within the active perovskite absorber and at its interfaces will be key to further progress in their development. Here we present a series of fully evaporated devices employing hole transport materials with different ionization energies. The open circuit voltage of the devices, along with their ideality factors, confirm that the former is mainly determined by the bulk and surface recombination in the perovskite, rather than by the energetic offset between the valence band of the perovskite and the highe…

Tuning Charge Carrier Dynamics and Surface Passivation in Organolead Halide Perovskites with Capping Ligands and Metal Oxide Interfaces

2018

Organolead halide perovskites have emerged as exciting optoelectronic materials but a complete understanding of their photophysical properties is still lacking. Here, a morphological series of methylammonium lead bromide (MAPbBr 3 ) perovskites are studied by transient optical spectroscopies over eight orders of magnitude in timescale to investigate the effect of nanostructuring and surface states on the charge carrier dynamics. The sample preparation route and corresponding morphology changes influence the position of the optical features, recombination dynamics, excitation fluence dependence, and dramatically impact surface trap passivation. Growth of the perovskite layer in the presence …

Ab initio quantum-chemical computations of the absorption cross sections of HgX2 and HgXY (X, y = Cl, Br, and I): Molecules of interest in the Earth'…

2018

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