Understanding the Mechanisms of Methylammonium-Induced Thermal Instability in Mixed-FAMA Perovskites.

Despite a recent shift toward methylammonium (MA)-free lead-halide perovskites for perovskite solar cells, high-efficiency formamidinium lead iodide (FAPbI3) devices still often require methylammonium chloride (MACl) as an additive, which evaporates away during the annealing process. In this article, it is shown that the residual MA+, however, triggers thermal instability. To investigate the possibility of an optimal concentration of MA+ that may improve thermal stability, the intrinsic thermal stability of pure FA, FA-rich, MA-rich, and pure MA perovskite films (FA1-xMAxPbI3, FAMA) is studied. The results show that the thermal stability of FAMA perovskites decreases with more MA+, under degradation conditions that isolate the intrinsic thermal stability of the material (i.e., without moisture and oxygen effects). X-ray diffraction (XRD), proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS), photoluminescence (PL) and UV-visible spectroscopy, and depth-profiling X-ray Photoelectron Spectroscopy (XPS) are employed to show that the observed trend is mainly due to the decomposition of the MA+ cation, as opposed to other effects such as the precursor solvent and film morphologies. It is also found that the surfaces of these FAMA films are MA+ rich, although this phenomenon does not appear to affect thermal stability. Finally, it is demonstrated that this trend is unaffected by the presence of Spiro-OMeTAD atop the film, and thus solar cell devices should preserve this trend.

CO2 electroreduction favors carbon isotope 12C over 13C and facilitates isotope separation.

We discovered that CO2 electroreduction strongly favors the conversion of the dominant isotope of carbon (12C) and discriminates against the less abundant, stable carbon 13C isotope. Both absorption of CO2 in the alkaline electrolyte and CO2 electrochemical reduction favor the lighter isotopologue. As a result, the stream of unreacted CO2 leaving the electrolyzer has an increased 13C content, and the depletion of 13C in the product is several times greater than that of photosynthesis. Using a natural abundance feed, we demonstrate enriching of the 13C fraction to ∼1.3% (i.e., +18%) in a single-pass reactor and propose a scalable and economically attractive process to yield isotopes of a commercial purity. Our finding opens pathways to both cheaper and less energy-intensive production of stable isotopes (13C, 15N) essential to the healthcare and chemistry research, and to an economically viable, disruptive application of electrolysis technologies developed in the context of sustainability transition.

Molecular Locking with All-Organic Surface Modifiers Enables Stable and Efficient Slot-Die-Coated Methyl-Ammonium-Free Perovskite Solar Modules.

The power conversion efficiency (PCE) of the state-of-the-art large-area slot-die-coated perovskite solar cells (PSCs) is now over 19%, but issues with their stability persist owing to significant intrinsic point defects and a mass of surface imperfections introduced during the fabrication process. Herein, the utilization of a hydrophobic all-organic salt is reported to modify the top surface of large-area slot-die-coated methylammonium (MA)-free halide perovskite layers. Bearing two molecules, each of which is endowed with anchoring groups capable of exhibiting secondary interactions with the perovskite surfaces, the organic salt acts as a molecular lock by effectively binding to both anion and cation vacancies, substantially enhancing the materials' intrinsic stability against different stimuli. It not only reduces the ingression of external species such as oxygen and moisture, but also suppresses the egress of volatile organic components during the thermal stability testing. The treated PSCs demonstrate efficiency of 19.28% (active area of 58.5 cm2 ) and 17.62% (aperture area of 64 cm2 ) for the corresponding mini-module. More importantly, unencapsulated slot-die-coated mini-modules incorporating the all-organic surface modifier show ≈80% efficiency retention after 7500 h (313 days) of storage under 30% relative humidity (RH). They also remarkably retain more than 90% of the initial efficiency for over 850 h while being measured continuously.

Reversible Photochromism in ⟨110⟩ Oriented Layered Halide Perovskite.

Extending halide perovskites' optoelectronic properties to stimuli-responsive chromism enables switchable optoelectronics, information display, and smart window applications. Here, we demonstrate a band gap tunability (chromism) via crystal structure transformation from three-dimensional FAPbBr3 to a ⟨110⟩ oriented FAn+2PbnBr3n+2 structure using a mono-halide/cation composition (FA/Pb) tuning. Furthermore, we illustrate reversible photochromism in halide perovskite by modulating the intermediate n phase in the FAn+2PbnBr3n+2 structure, enabling greater control of the optical band gap and luminescence of a ⟨110⟩ oriented mono-halide/cation perovskite. Proton transfer reaction-mass spectroscopy carried out to precisely quantify the decomposition product reveals that the organic solvent in the film is a key contributor to the structural transformation and, therefore, the chromism in the ⟨110⟩ structure. These intermediate n phases (2 ≤ n ≤ ∞) stabilize in metastable states in the FAn+2PbnBr3n+2 system, which is accessible via strain or optical or thermal input. The structure reversibility in the ⟨110⟩ perovskite allowed us to demonstrate a class of photochromic sensors capable of self-adaptation to lighting.

Nonintubated Tracheal Surgery.

The article describes an anesthetic management strategy for resection of the cervical trachea due to benign stenosis without using an endotracheal tube. The strategy includes: (1) insertion of an airway stent in the stenotic area, (2) insertion of a supraglottic airway device (SGAD), and (3) advancing a jet ventilation catheter through the SGAD. The stent is removed during surgery together with the resected part of the trachea. The technique of nonintubated tracheal resection allows the surgeon to work most comfortably and helps the anesthesiologist properly maintain the patient's vital functions in the operating room.

Complete mitochondrial genome of the white char Salvelinus albus (Salmoniformes, Salmonidae).

The complete mitochondrial genome was sequenced in two individuals of white char Salvelinus albus. The genome sequences are 16 653 bp in size, and the gene arrangement, composition, and size are very similar to the salmonid fish genomes published previously. The low level of sequence divergence detected between the genome of S. albus and the GenBank complete mitochondrial genomes of the Northern Dolly Varden char S. malma (KJ746618) and the Arctic char S. alpinus (AF154851) may likely be due to recent divergence of the species and/or historical hybridization and interspecific replacement of mtDNA.

5,6,7,8-Tetrafluoro-3lambda4delta2,1,2,4-benzothiaselenadiazine, 5,6,7,8-tetrafluoro-1,3lambda4delta2,2,4-benzodithiadiazine, and their hydrocarbon analogues: molecular and crystal structures.

5,6,7,8-Tetrafluoro-3lambda4delta2,1,2,4-benzothiaselenadiazine (1) is prepared by the intramolecular nucleophilic cyclization of C6F5SeN=S=NSiMe3 (2) mediated by CsF. According to an X-ray diffraction analysis, the heterocycle of 1 is bent along the Se(1)...N4 line by 6.0(2) degrees in the crystal. Despite the obvious similarities between 1 and its 1,3-dithia analogue (7) with respect to molecular composition and shape, the crystal packing of 1 is substantially different from that of 7. An interesting consequence of this is the inclusion of atmospheric N2 in the crystal lattice of the selenium derivative 1. The molecular structure and bonding of 1 have been investigated using quantum-chemical calculations at the DFT/B3LYP/6-311+G level of theory, and the results have been compared to those of 5,6,7,8-tetrafluoro-1,3lambda4delta2,2,4-benzodithiadiazine (7) and their hydrocarbon analogues (5 and 8).

Does a stabilising interaction favouring the Z,Z configuration of -S-N=S=N-S- systems exist?

The existence of the orbital interaction presented in the literature as being the cause for the stabilisation of the Z,Z configuration of Ph-S-N=S=N-S-Ph (1) and its derivatives in the crystal phase, has been investigated. The results of theoretical calculations at the DFT/B3LYP/6-311+G* level of theory suggest that such a stabilising interaction might not exist or be extremely weak and that packing forces must be the main cause of the observed Z,Z configuration in the solid. To reach this conclusion structural and energetic parameters were combined to study the bonding in these -S-N=S=N-S- systems. For the analogous Ph-Se-N=S=N-Se-Ph (2) in particular the isomeric equilibrium in solution found in the variable-temperature 77Se NMR spectrum indicates that, in the gas phase or in solution, the observed Z,Z configuration is not stabilised to a greater extent than the Z,E configuration.