Mixed lead–tin perovskite films with >7 μs charge carrier lifetimes realized by maltol post-treatment

Mixed lead–tin (Pb–Sn) halide perovskites with optimum band gaps near 1.3 eV are promising candidates for next-generation solar cells. However, the performance of solar cells fabricated with Pb–Sn perovskites is restricted by the facile oxidation of Sn(ii) to Sn(iv), which induces self-doping. Maltol, a naturally occurring flavor enhancer and strong metal binding agent, was found to effectively suppress Sn(iv) formation and passivate defects in mixed Pb–Sn perovskite films. When used in combination with Sn(iv) scavenging, the maltol surface treatment led to high-quality perovskite films which showed enhanced photoluminescence intensities and charge carrier lifetimes in excess of 7 μs. The scavenging and surface treatments resulted in highly reproducible solar cell devices, with photoconversion efficiencies of up to 21.4% under AM1.5G illumination.

Maltol, a metal binding agent, effectively passivates defects on the surface of mixed lead–tin perovskite films. The carrier lifetimes of the resultant perovskite films are over 7 μs. The solar cell devices exhibit efficiencies of up to 21.4%.     

Intramolecular hydrosilation of acetylenes: Regioselective functionalization of homopropargyl alcohols

Platinum-catalyzed intramolecular hydrosilation of hydrodimethylsilyl ethers of homopropargyl alcohols proceeds regioselectively in a 5-exo-dig mode. The resulting vinylsilanes can be transformed into 3-alkanon-1-ol and 3-bromo-3-alken-1-ol derivatives by H₂O₂ oxidation and bromine cleavage, respectively.     

Reactivities of cellulases from fungi towards ribbon-type bacterial cellulose and band-shaped bacterial cellulose

We have investigated the reactivities of various cellulases onribbon-type bacterial cellulose (BC I) and band-shaped bacterial cellulose (BCII) so as to clarify the properties of different cellulases. BC I waseffectively hydrolyzed by exo-type cellulases from different fungi from twicetofour times as much as BC II, but endo-type cellulases showed little differencein reactivity on those substrates. One of the endo-type cellulases, EG II fromTrichoderma reesei, degraded BC II more rapidly thanexo-type cellulases even in the production of reducing sugars. The degree ofpolymerization (DP) of BC II was rapidly decreased by endo-type cellulases atanearly stage, while exo-type cellulases did not cause the decrease of DP atthe initial stage, though the decrease of DP was observed after an incubation of24 h. All exo-type cellulases adsorbed on BC I and BC II,whileendo-type cellulases except for EG II adsorbed slightly on both substrates. Itwas interesting to observe EG II adsorbed on BC I but not on BC II. It issuggested that the adsorption of enzyme on cellulose is important for thedegradation of BC I, but not for BC II. It is proposed that the ratio of aspecific activity of each enzyme between BC I and BC II represents thedifference in the mode of action of cellulase. Furthermore, the K _RW value, which we can calculate from thedecrease of DP/reducing sugar produced, is effective for discriminating themode of action of cellulase, especially the evaluation of randomness in thehydrolysis of cellulose by endo- and exo-type cellulases.     

Time-resolved structural studies in fiber processing

Time-resolved and off-line synchrotron wide-angle and small-angle x-ray scattering (WAXS and SAXS) was used to study the structure formation in poly-p-phenylenebenzobisoxazole (PBO) fibers during various stages of spinning, coagulation, and heating processes. WAXS data could be explained in terms of liquid-crystalline structures of varying degrees of order. A structure model is proposed that is in accordance with the observed SAXS four-point pattern.     

Synthetic application of tributylstannyl ester of silicic acid: Synthesis and polymerization of polysiloxane having methacryloyloxypropyl groups

Polymeric tributylstannyl ester of silicic acid ( PTBS ) was demonstrated to be a useful intermediary compound for the preparation of polysiloxane derivative ( MPS ), which possessed methacryloyloxypropyl groups. The reaction of PTBS and (3-methacryloyloxypropyl)dimethylchlorosilane ( 1a ) proceeded readily at room temperature under neutral conditions to give MPS with the elimination of tributyltin group. The reaction conducted in the presence of 1a and trimethylchlorosilane ( 1b ) was effective for the preparation of MPS containing the both silyl groups, in which the content of methacryloyloxy groups could be controlled. The obtained MPS polymerized readily under UV irradiation to afford the organic–inorganic hybrid resin ( MSR ) as a kind of organically modified silica gel. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4226–4232, 1999     

Single-Step Construction of a Nine-Membered Carbocycle by a New [4+4+1] Cycloaddition

A palladium catalyst serves as a template for the assembly of a nine-membered carbocycle from two molecules of vinylallene and one molecule of carbon monoxide [Eq. (a)]. This unprecedented [4+4+1] cycloaddition is in marked contrast to the [4+1] cycloaddition mediated by rhodium(I ) catalysts.     

Toward Pluramycins with Epoxy Side Chain: Syntheses of Kidamycinone and Epoxykidamycinone (Saptomycinone H)

For exploring general routes to the pluramycin‐class of antibiotics, including congeners with epoxide‐bearing side chains, syntheses of kidamycinone and its epoxide (epoxykidamycinone) have been achieved. At the stage of the A‐ring cyclization with alkene‐bearing side chain, the desired 6‐endo product was obtained as a major compound, although the corresponding undesired 5‐exo product was also formed.     

Conversion of Molecular Oxygen into a Hydroperoxo Species by Ring-Opening Protonation of a Cyclic η2-Peroxo Intermediate: Characterization of the η2-Peroxo and Hydroperoxo Complexes

A transition metal–hydroperoxo species is formed by the oxygenation of a low-valent rhodium precursor followed by a protonation of the resulting η²-O₂ ligand; the latter process is assisted by an intramolecular hydrogen-bonding interaction (see scheme). This process is the first structural evidence for an effective method for the activation of molecular oxygen as postulated for the cytochrome P-450 system.     

Poly(phenylhydrosilane): Base-developable polysilane resist

Poly(phenylhydrosilane) becomes soluble in a 2.38% tetramethylammoniumhydroxide aqueous solution after exposure to UV light. This is the first report that the polysilanes not bearing acidic groups can be developed with dilute basic aqueous solutions. Addition of 3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone increases the resist sensitivity. The reaction mechanism is as follows: PS1 photodecomposes to form silyl compounds having SiOH groups, which become soluble in an aqueous base solution, because these silane compounds bearing SiOHs are acidic. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2355–2364, 1997