Recently, solution-processable organic-inorganic metal halide perovskites have come to the fore as a result of their high power-conversion efficiencies (PCE) in photovoltaics, exceeding 17%. To attain reproducibility in the performance, one of the critical factors is the processing conditions of the perovskite film, which directly influences the photophysical properties and hence the device performance. Here we study the effect of annealing parameters on the crystal structure of the perovskite films and correlate these changes with its photophysical properties. We find that the crystal formation is kinetically driven by the annealing atmosphere, time and temperature. Annealing in air produces an improved crystallinity and large grain domains as compared to nitrogen. Lower photoluminescence quantum efficiency (PLQE) and shorter photoluminescence (PL) lifetimes are observed for nitrogen annealed perovskite films as compared to the air-annealed counterparts. We note that the limiting nonradiative pathways (i.e., maximizing PLQE) is important for obtaining the highest device efficiency. This indicates a critical impact of the atmosphere upon crystallization and the ultimate device performance.

Wide-angle X-ray scattering (WAXS) 2D layered data and time-traces of individual diffraction peak of a FA0.83Cs0.17Pb(I0.6Br0.4)3 perovskite film fabricated with a low-temperature DMF/DMSO and a high-temperature DMF/Acid fabrication method. The data shows the first 5 minutes of a FA0.83Cs0.17Pb(I0.6Br0.4)3 perovskite film fabricated with the A, C, E) DMF/DMSO fabrication method annealed at 100  C B, E, F) DMF/Acid fabrication method annealed at 185  C. The DMF/Acidmethod was prepared with a "fully-aged" solution, which was aged for more than 72h after the addition of the HI/HBr additive. Annealing was done in a helium atmosphere with slight water/oxygen contamination.

Tissue engineering benefits from novel materials with precisely tunable physical, chemical and mechanical properties over a broad range. Here we report a practical approach to prepare Bombyx mori silk fibroin hydrogels using the principle of non-solvent induced phase separation (NIPS). A combination of reconstituted silk fibroin (RSF) and methanol (non-solvent), with a final concentration of 2.5% w/v and 12.5% v/v respectively, maintained at 22 °C temperature turned into a hydrogel within 10 hours. Freeze-drying of this gel gave a foam with a porosity of 88%, a water uptake capacity of 89% and a swelling index of 8.6. The gelation kinetics and the loss tangent of the gels were investigated by rheometry. The changes in the morphology of the porous foams were visualized by SEM. The changes in RSF chemical composition and the relative fraction of its secondary structural elements were analyzed by ATR-FTIR along with Fourier self-deconvolution. And, the changes in the glass transition temperature, specific heat capacity and the relative fraction of crystallinity of RSF were determined by TM-DSC. Data suggested that RSF-water-methanol behaved as a polymer-solvent-non-solvent ternary phase system, wherein the demixing of the water-methanol phases altered the thermodynamic equilibrium of RSF-water phases and resulted in the desolvation and eventual separation of the RSF phase. Systematic analysis revealed that both gelation time and the properties of hydrogels and porous foams could be controlled by the ratios of RSF and non-solvent concentration as well as by the type of non-solvent and incubation temperature. Due to the unique properties we envisage that the herein prepared NIPS induced RSF hydrogels and porous foams can possibly be used for the encapsulation of cells and/or for the controlled release of both hydrophilic and hydrophobic drugs.

It was recently discovered that transparent microspheres and cylinders can function as a super-resolution lens (i.e., superlens) to focus light beyond the diffraction limit. A number of high-resolution applications based on these lenses have been successfully demonstrated and span nanoscopy, imaging, and spectroscopy. Fabrication of these superlenses, however, is often complex and requires sophisticated engineering processes. Clearly an easier model candidate, such as a naturally occurring superlens, is highly desirable. Here, we report for the first time a biological superlens provided by nature: the minor ampullate spider silk spun from the Nephila spider. This natural biosuperlens can distinctly resolve 100 nm features under a conventional white-light microscope with peak wavelength at 600 nm, attaining a resolution of λ/6 that is well beyond the classical limit. Thus, our work opens a new door to develop biology-based optical systems that may provide a new solution to integrating optics in biological systems.

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