Influence of layer thickness on the power conversion efficiency of tin halide-based planar heterojunction solar cells

In recent years, perovskite-based solar cell technologies have sparked much interest. Organic-inorganic halide perovskites (OIHPs) are a type of perovskite that has shown promise in various optoelectronic applications. The power conversion efficiency (PCE) of organic-inorganic perovskite materials is improving with new materials development. However, inorganic materials studied in labs have limited PCE. Lead-free tin halide CH3NH3SnX3 shows good PCE. In this work, we study the electrical characteristics of tin halide as a perovskite absorbing layer in planar heterojunction solar cells with the help of GPVDM solar cell simulation software. A comparative study of power conversion efficiency has been done for tin halide of chloride, bromide, and iodide. The effect of electron and hole drift-diffusion, carrier continuity equations in position space to represent charge flow within the device, Poisson's equation, and charge carrier recombination has been studied in detail.

Open-Cage Fullerene as Molecular Container for F- , Cl- , Br- and I. Angew Chem Int Ed Engl 2022;61:e202212090. [PMID: 36316627 DOI: 10.1002/anie.202212090]

A 19-membered open-cage fullerene derivative was prepared from C₆₀ in 7 steps and 5.5 % yield through the peroxide-mediate pathway. There are four carbonyl groups, an ether oxygen and a quinoxaline moiety on the rim of the orifice. A chloride anion could be inserted into its cavity by heating with hydrochloric acid at 60 °C for 4 h. Encapsulation of fluoride, bromide and iodide anions was also achieved at slightly more forcing conditions, 90 °C for 14 h. Single crystal X-ray structures of the sodium salt of the chloride and the bromide encapsulated derivatives were obtained, which showed the halide anion in the center of the cavity and two sodium cations connecting two cages through coordination to the oxygen atoms on the rim of the orifices. The halide encapsulation ratio is quantitative in the isolated products.

Pressure-Induced Phase Transition, Jahn-Teller Suppression, Optical and Electronic Property Evolutions in Ruddlesden-Popper Perovskites Rb2 CuCl4-x Brx

Transition-metal containing halides with Ruddlesden-Popper (RP) perovskite structures have received extensive attention owing to their emerging and anisotropic photoelectric functionalities. Among them, A₂ CuX₄ (A=alkali metal or organic cations, X=Cl, Br, I) series are particular, because of the Jahn-Teller distortion of Cu²⁺ sensitive to external stimuli such as temperature and pressure. In this article, we report the structure evolution and physical property responses of RP perovskites Rb₂ CuCl_4-x Br_x (x=1, 2) to external pressure. Dramatic structural phase transitions from orthorhombic to monoclinic occur around 3.0 GPa in both materials regardless of their distinct compositions. Structure analyses reveal the suppression and final vanishing of the Jahn-Teller distortion of Cu²⁺ cations under compression and crossing the phase transition, respectively. Rb₂ CuCl_4-x Br_x perovskites exhibit abrupt bandgap narrowing (from reddish-brown to black) along with the structural phase transition, and an overall bandgap narrowing of 75% up to ∼27 GPa but still keeping semiconductive. During the compression processes, the resistances of Rb₂ CuCl_4-x Br_x have been greatly reduced by 5-orders of magnitude. Moreover, all of the pressure-induced phenomena in Rb₂ CuCl_4-x Br_x perovskites are reversible upon decompression and no obvious difference is observed for the pressure responses between [CuCl₄ Br₂ ] and [CuCl₄ (Cl,Br)₂ ] coordination environments. The impact of pressure on the structural and physical properties in two-dimensional Rb₂ CuCl_4-x Br_x provides in-depth understanding on the structure design of functional halide perovskites at ambient conditions.

Modeling of lattice parameters of cubic perovskite oxides and halides

Perovskites having the chemical formulae of ABX3 are promising candidates for various electronic, magnetic, and thermal applications. One of the important structural factors is a (the lattice constant), which represents the unit cell size. The variation in the lattice constant is a combined result of interactions between different ions, determined by valence electrons and ionic radii. The size and stability of unit cells have important influences on structural stabilities, bandgap structures, and therefore performance of materials. To obtain the lattice constant of cubic perovskites without going through experimental efforts such as synthesis and measurements, we construct a model based on Gaussian process regressions for cubic perovskite lattice constant predictions. The model utilizes the number of valence electrons as well as ionic radii of alloying elements as predictors. A total of 149 cubic perovskites containing fluorides, chlorides, and bromides with cation combinations of A1+B2+, as well as oxides with cation combinations of A1+B5+, A2+B4+, and A3+B3+ are explored. The model demonstrates good performance in terms of stabilities and accuracy, and thus could be a rapid approach to estimate lattice constants.

The photocatalytic destruction of cinnamic acid and cinnamyl alcohol: Mechanism and the effect of aqueous ions

Cinnamic acid was chosen as an exemplar molecule to study the effect of potential contaminants on the kinetics and mechanism of the photocatalytic destruction of hydrocarbons in aqueous solutions. We identify the principal intermediates in the photocatalytic reaction of the acid and corresponding alcohol, and propose a mechanism that explains the presence of these species. The impact of two likely contaminants of aqueous systems, sulfate and chloride ions were also studied. Whereas sulfate ions inhibit the degradation reaction at all concentrations, chloride ions, up to a concentration of 0.5 M, accelerate the removal of cinnamic acid from solution by a factor of 1.6. However, although cinnamic acid is removed, the pathway to complete oxidation is blocked by the chloride, with the acid being converted (in the presence of oxygen) into new products including acetophenone, 2-chloroacetophenone, 1-(2-chlorophenyl)ethenone and 1,2-dibenzoylethane. We speculate that the formation of these products involves chlorine radicals formed from the reaction of chloride ions with the photoinduced holes at the catalyst surface. Interestingly, we have shown that the 1-(2-chlorophenyl)ethenone and 1,2-dibenzoylethane products form from 2-chloroacetophenone when irradiated with 365 nm light in the absence of the catalyst. The formation of potentially dangerous side products in this reaction suggest that the practical implementation of the photocatalytic purification of contaminated water needs to considered very carefully if chlorides are likely to be present.

Experimental rainwater divalent mercury speciation and photoreduction rates in the presence of halides and organic carbon

Mercury (Hg) photochemical redox reactions control atmospheric Hg lifetime and therefore play an important role in global Hg cycling. Oxidation of Hg(0) to Hg(II) is currently thought to be a Br-initiated two-stage reaction with end-products HgBr₂, HgBrOH, HgBrONO, HgBrOHO. Atmospheric photoreduction of these Hg(II) compounds can take place in both the gas and aqueous phase. Here we present new experimental observations on aqueous Hg(II) photoreduction rates in the presence of dissolved organic carbon and halides and compare the findings to rainfall Hg(II) photoreduction rates. The pseudo first-order, gross photoreduction rate constant, k_red, for 0.5 μM Hg(II) in the presence of 0.5 mg/ L of dissolved organic carbon (DOC) is 0.23 h^-1, which is similar to the mean k_red (0.15 ± 0.01 h^-1(σ, n = 3)) in high altitude rainfall and at the lower end of the median k_red (0.41 h^-1, n = 24) in continental and marine waters. Addition of bromide (Br^-) to experimental Hg(II)-DOC solutions progressively inhibits Hg(II) photoreduction to reach 0.001 h^-1 at total Br^- of 10 mM. Halide substitution experiments give Hg(II)X_n^(n-2) photoreduction rate constants of 0.016, 0.004 h^-1, and < detection limit for X = Cl^-, Br^-, and I^- respectively and reflect increasing stability of the Hg(II)-halide complex. We calculate equilibrium Hg(II) speciation in urban and high-altitude rainfall using Visual Minteq, which indicates Hg(II)-DOC to be the dominant Hg species. The ensemble of observations suggests that atmospheric gaseous HgBr₂, HgCl₂, HgBrNO₂, HgBrHO₂ forms, scavenged by aqueous aerosols and cloud droplets, are converted to Hg(II)-DOC forms in rainfall due to abundant organic carbon in aerosols and cloud water. Eventual photoreduction of Hg(II)-DOC in aqueous aerosols and clouds is, however, too slow to be relevant in global atmospheric Hg cycling.

N-terminal residues are crucial for quaternary structure and active site conformation for the phosphoserine aminotransferase from enteric human parasite E. histolytica

Phosphoserine aminotransferase (PSAT) is a pyridoxal-5'phosphate (PLP)-dependent enzyme that catalyzes the second reversible step in the phosphoserine biosynthetic pathway producing serine. The crystal structure of E. histolytica PSAT (EhPSAT) complexed with PLP was elucidated at 3.0 Å resolution and the structures of its mutants, EhPSAT_Δ45 and EhPSAT_Δ4, at 1.8 and 2.4 Å resolution respectively. Deletion of 45 N-terminal residues (EhPSAT_Δ45) resulted in an inactive protein, the structure showed a dimeric arrangement drastically different from that of the wild-type protein, with the two monomers translated and rotated by almost 180° with respect to each other; causing a rearrangement of the active site to which PLP was unable to bind. Deletion of first N-terminal 15 (EhPSAT_Δ15) and four 11th to 14th residues (EhPSAT_Δ4) yielded up to 98% and 90% decrease in the activity respectively. Absence of aldimine linkage between PLP-Lys in the crystal structure of EhPSAT_Δ4 mutant explains for such decrease in activity and describes the importance of these N-terminal residues. Furthermore, a halide-binding site was found in close proximity to the active site. A stretch of six amino acids (146-NNTIYG-151) only conserved in the Entamoeba genus, contributes to halide binding may explain that the halide inhibition could be specific to Entamoeba.

Application of ESI-HRMS for molybdenum speciation in natural waters: An investigation of molybdate-halide reactions

High resolution electrospray ionization mass spectrometry (ESI-HRMS) was used to study the speciation of molybdate in interaction with halides (Cl, F, Br). Desolvation during electrospray ionization induced alteration of aqueous species but method optimization successfully suppressed artefact compounds. At low Mo concentrations, chloro(oxo)molybdate and fluoro(oxo)molybdate species were found and in natural samples, MoO₃Cl was detected for the first time, to the best of our knowledge. Apparent equilibrium constants for Cl substitution on molybdate were calculated for a range of pH values from 4.5 to 8.5. A minor alteration in speciation during the gas phase (conversion of doubly charged MoO₄^2- to HMoO₄^-) did not allow investigation of the molybdate acid-base properties; however this could be determined by speciation modeling. This study provides further evidence that ESI-HRMS is a fast and suitable tool to Deceasedassess the speciation of inorganic compounds such as Mo.

Halide removal from aqueous solution by novel silver-polymeric materials

The objective of this study was to analyze the behavior of a new material, silver-doped polymeric cloth (Ag-cloth), in the removal of bromide and iodide from waters. Silver is immobilized on the cloth, guaranteeing selective adsorption of the halide ions as retained silver halides that therefore do not pass into the solution. Results indicate that Ag⁰ reacts with H₂O₂ in the first phases of the process, yielding Ag⁺ and superoxide radical; however, as the process advances, this radical favors Ag⁺ reduction. Increases in the concentration of H₂O₂ augment the capacity of the Ag-cloth to remove halides from the medium up to a maximum concentration (55μM), above which the removal capacity remains constant (Xm≅1.3-1.8mg halide/g Ag-cloth). Thus, when there is excess H₂O₂ in the medium, secondary competitive reactions that take place in the process guarantee a constant Ag⁺ concentration, which defines the maximum adsorption capacity of Ag-cloth, reducing its ability to remove halides. Ag-cloth has a higher capacity to remove iodide than bromide, and the presence of organic matter or chloride reduces its capacity to remove iodide or bromide from water. The results obtained shown that the capacity of Ag⁰ with H₂O₂ significantly varies as a function of the medium pH from 1mg Br^-/g Ag-cloth at very low pH to 1.6mg/g Ag-cloth at pH9.

Photon Transport in One-Dimensional Incommensurately Epitaxial CsPbX3 Arrays

One-dimensional nanoscale epitaxial arrays serve as a great model in studying fundamental physics and for emerging applications. With an increasing focus laid on the Cs-based inorganic halide perovskite out of its outstanding material stability, we have applied vapor phase epitaxy to grow well aligned horizontal CsPbX₃ (X: Cl, Br, or I or their mixed) nanowire arrays in large scale on mica substrate. The as-grown nanowire features a triangular prism morphology with typical length ranging from a few tens of micrometers to a few millimeters. Structural analysis reveals that the wire arrays follow the symmetry of mica substrate through incommensurate epitaxy, paving a way for a universally applicable method to grow a broad family of halide perovskite materials. The unique photon transport in the one-dimensional structure has been studied in the all-inorganic Cs-based perovskite wires via temperature dependent and spatially resolved photoluminescence. Epitaxy of well oriented wire arrays in halide perovskite would be a promising direction for enabling the circuit-level applications of halide perovskite in high-performance electro-optics and optoelectronics.