A Purified, Solvent-Intercalated Precursor Complex for Wide-Process-Window Fabrication of Efficient Perovskite Solar Cells and Modules.

A high-purity methylammonium lead iodide complex with intercalated dimethylformamide (DMF) molecules, CH3 NH3 PbI3 ⋅DMF, is introduced as an effective precursor material for fabricating high-quality solution-processed perovskite layers. Spin-coated films of the solvent-intercalated complex dissolved in pure dimethyl sulfoxide (DMSO) yielded thick, dense perovskite layers after thermal annealing. The low volatility of the pure DMSO solvent extended the allowable time for low-speed spin programs and considerably relaxed the precision needed for the antisolvent addition step. An optimized, reliable fabrication method was devised to take advantage of this extended process window and resulted in highly consistent performance of perovskite solar cell devices, with up to 19.8 % power-conversion efficiency (PCE). The optimized method was also used to fabricate a 22.0 cm2 , eight-cell module with 14.2 % PCE (active area) and 8.64 V output (1.08 V/cell).

Influence of Alkoxy Chain Length on the Properties of Two-Dimensionally Expanded Azulene-Core-Based Hole-Transporting Materials for Efficient Perovskite Solar Cells.

A series of two-dimensionally expanded azulene-core-based π systems have been synthesized with different alkyl chain lengths in the alkoxy moieties connected to the partially oxygen-bridged triarylamine skeletons. The thermal, photophysical, and electronic properties of each compound were evaluated to determine the influence of the alkyl chain length on their effectiveness as hole-transporting materials (HTMs) in perovskite solar cells (PSCs). All the synthesized molecules showed promising material properties, including high solubility, the formation of flat and amorphous films, and optimal alignment of energy levels with perovskites. In particular, the derivatives with methyl and n-butyl in the side chains retained amorphous stability up to 233 and 159 °C, respectively. Such short alkoxy chains also resulted in improved electrical device properties. The PSC device fabricated with the HTM with n-butyl side chains showed the best performance with a power conversion efficiency of 18.9 %, which compares favorably with that of spiro-OMeTAD-based PSCs (spiro-OMeTAD=2,2',7,7'-tetrakis[N,N-bis(p-methoxyphenyl)amino]-9,9'-spirobifluorene).

Lead-Free Solar Cells based on Tin Halide Perovskite Films with High Coverage and Improved Aggregation.

Two simple methods to improve tin halide perovskite film structure are introduced, aimed at increasing the power conversion efficiency of lead free perovskite solar cells. First, a hot antisolvent treatment (HAT) was found to increase the film coverage and prevent electrical shunting in the photovoltaic device. Second, it was discovered that annealing under a low partial pressure of dimethyl sulfoxide vapor increased the average crystallite size. The topographical and electrical qualities of the perovskite films are substantively improved as a result of the combined treatments, facilitating the fabrication of tin-based perovskite solar cell devices with power conversion efficiencies of over 7 %.

Solvent-Coordinated Tin Halide Complexes as Purified Precursors for Tin-Based Perovskites.

A series of solvent-coordinated tin halide complexes were prepared as impurity-free precursors for tin halide perovskites, and their structures were determined by single-crystal X-ray diffraction analysis. Using these precursors, the tin halide perovskites, MASnI3 and FASnI3, were prepared, and their electronic structures and photophysical properties were examined under inert conditions by means of photoelectron yield spectroscopy as well as absorption and fluorescence spectroscopies. Their valence bands (MASnI3: -5.02 eV; FASnI3: -5.16 eV) are significantly higher than those of MAPbI3 or the typical hole-transporting materials 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene and poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine). These results suggest that to develop the solar cells using these tin halide perovskites with efficient hole-collection properties, hole-transporting materials should be chosen that have the highest occupied molecular orbital levels higher than -5.0 eV.

Structure, activity, and stability of metagenome-derived glycoside hydrolase family 9 endoglucanase with an N-terminal Ig-like domain.

A metagenome-derived glycoside hydrolase family 9 enzyme with an N-terminal immunoglobulin-like (Ig-like) domain, leaf-branch compost (LC)-CelG, was characterized and its crystal structure was determined. LC-CelG did not hydrolyze p-nitrophenyl cellobioside but hydrolyzed CM-cellulose, indicating that it is endoglucanase. LC-CelG exhibited the highest activity at 70°C and >80% of the maximal activity at a broad pH range of 5-9. Its denaturation temperature was 81.4°C, indicating that LC-CelG is a thermostable enzyme. The structure of LC-CelG resembles those of CelD from Clostridium thermocellum (CtCelD), Cel9A from Alicyclobacillus acidocaldarius (AaCel9A), and cellobiohydrolase CbhA from C. thermocellum (CtCbhA), which show relatively low (29-31%) amino acid sequence identities to LC-CelG. Three acidic active site residues are conserved as Asp194, Asp197, and Glu558 in LC-CelG. Ten of the thirteen residues that form the substrate binding pocket of AaCel9A are conserved in LC-CelG. Removal of the Ig-like domain reduced the activity and stability of LC-CelG by 100-fold and 6.3°C, respectively. Removal of the Gln40- and Asp99-mediated interactions between the Ig-like and catalytic domains destabilized LC-CelG by 5.0°C without significantly affecting its activity. These results suggest that the Ig-like domain contributes to the stabilization of LC-CelG mainly due to the Gln40- and Asp99-mediated interactions. Because the LC-CelG derivative lacking the Ig-like domain accumulated in Escherichia coli cells mostly in an insoluble form and this derivative accumulated in a soluble form exhibited very weak activity, the Ig-like domain may be required to make the conformation of the active site functional and prevent aggregation of the catalytic domain.

Structure and stability of metagenome-derived glycoside hydrolase family 12 cellulase (LC-CelA) a homolog of Cel12A from Rhodothermus marinus.

Ten genes encoding novel cellulases with putative signal peptides at the N-terminus, termed pre-LC-CelA-J, were isolated from a fosmid library of a leaf-branch compost metagenome by functional screening using agar plates containing carboxymethyl cellulose and trypan blue. All the cellulases except pre-LC-CelG have a 14-29 residue long flexible linker (FL) between the signal peptide and the catalytic domain. LC-CelA without a signal peptide (residues 20-261), which shows 76% amino acid sequence identity to Cel12A from Rhodothermus marinus (RmCel12A), was overproduced in Escherichia coli, purified and characterized. LC-CelA exhibited its highest activity across a broad pH range (pH 5-9) and at 90 °C, indicating that LC-CelA is a highly thermostable cellulase, like RmCel12A. The crystal structure of LC-CelA was determined at 1.85 Å resolution and is nearly identical to that of RmCel12A determined in a form without the FL. Both proteins contain two disulfide bonds. LC-CelA has a 16-residue FL (residues 20-35), most of which is not visible in the electron density map, probably due to structural disorder. However, Glu34 and Pro35 form hydrogen bonds with the central region of the protein. ΔFL-LC-CelA (residues 36-261) and E34A-LC-CelA with a single Glu34 â†’ Ala mutation were therefore constructed and characterized. ΔFL-LC-CelA and E34A-LC-CelA had lower melting temperatures (T m) than LC-CelA by 14.7 and 12.0 °C respectively. The T m of LC-CelA was also decreased by 28.0 °C in the presence of dithiothreitol. These results suggest that Glu34-mediated hydrogen bonds and the two disulfide bonds contribute to the stabilization of LC-CelA.