A chemically inert bismuth interlayer enhances long-term stability of inverted perovskite solar cells.

Long-term stability remains a key issue impeding the commercialization of halide perovskite solar cells (HPVKSCs). The diffusion of molecules and ions causes irreversible degradation to photovoltaic device performance. Here, we demonstrate a facile strategy for producing highly stable HPVKSCs by using a thin but compact semimetal Bismuth interlayer. The Bismuth film acts as a robust permeation barrier that both insulates the perovskite from intrusion by undesirable external moisture and protects the metal electrode from iodine corrosion. The Bismuth-interlayer-based devices exhibit greatly improved stability when subjected to humidity, thermal and light stresses. The unencapsulated device retains 88% of its initial efficiency in ambient air in the dark for over 6000 h; the devices maintain 95% and 97% of their initial efficiencies after 85 °C thermal aging and light soaking in nitrogen atmosphere for 500 h, respectively. These sound stability parameters are among the best for planar structured HPVKSCs reported to date.

Functionalized Graphene Oxide Enables a High-Performance Bulk Heterojunction Organic Solar Cell with a Thick Active Layer.

Novel functionalized graphene oxide π-π stacking with conjugated polymers (P-GO) is fabricated via a simple ethanol-mediated mixing method, leading to better dispersion in organic nonpolar solvents and bypassing the inherent restrictions of hydrophilicity and oleophobicity. We analyze the mechanism of the incorporation of P-GO into inverted organic solar cells (OSCs) based on a poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4- b]thiophenediyl]] (PTB7):[6,6]-phenyl C71 butyric acid methyl ester (PC71BM) system to investigate the possibility of high-performance thick-film OSC fabrication. It is verified that the incorporation of P-GO into the PTB7:PC71BM blend films leads to a decreased π-π stacking distance, enlarged coherence length for polymer, and optimized phase separation, resulting in more effective charge dissociation, reduced bimolecular recombination, and more balanced charge transport. The OSCs with 1% P-GO incorporation demonstrate a thickness-insensitive fill factor (57.8%) and power conversion efficiency (PCE) (7.31%) even with 250 nm thick photoactive layers, leading to a dramatic PCE enhancement of 34% compared with the control devices with the same thickness.

Synthesis, Characterization and Antimicrobial Activities of Copper Derivatives of NHC-II Complexes.

BACKGROUND: Caffeine, 1, 3, 7-trimethylxanthine is one of the xanthine derivatives that are for the most part utilized as a part of solutions as diuretics. The Cu (II) complexes have been synthesized from the N-heterocyclic carbene ligands. MATERIALS AND METHODS: The Cu (II) NHC complexes were characterized using analytical and spectral techniques. Antibacterial and antifungal activities of the Cu (II) NHC complexes were determined using the reported techniques. The SOD activity was assayed using nitrobluetetrazolium as O2 scavenger. RESULTS: The X-band ESR spectra of the copper complexes in DMSO solution at 300 and 77 K were recorded and their salient features are reported. The in vitro biological screening effects of the investigated compounds were tested against the bacterial species, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris and Pseudomonas aeruginosa and fungal species, Aspergillus niger, Rhizopus stolonifer, Aspergillus flavus, Rhizoctonia bataicola and Candida albicans by serial dilution method. CONCLUSION: The Cu (II) complexes exhibit square planar geometry. A comparative study of inhibition values of the individual metals and their complexes indicate that the complexes exhibit higher antimicrobial activity than the individual metals. Superoxide dismutase and reducing power activities of the copper complexes have also been studied. Depending on the molecular structure, the Cu (II) NHC complex possess promising SOD mimetic activities. Further we are trying to explore more biological properties of Cu (II) NHC complexes in vitro and in vivo.

Femtosecond laser written nanostructures in Ge-doped glasses.

We report on nanostructures induced by femtosecond laser pulses in the bulk of Germanium-doped silica glasses. For studying structural properties of the nanostructure constituents small-angle x-ray scattering and SEM served to map pore size, filling factor and periodicity. Our results show that with increasing the Ge doping concentration, the aspect ratio (transverse to inscribing laser) of nanometric pores rises while they arrange in a smaller period in contrast to nanogratings in pristine fused silica. Consequently, higher optical retardance can be obtained demonstrating the pronounced glass decomposition due to the changing network structure.

Synthesis, spectral characterization, electron microscopic study and thermogravimetric analysis of a phosphorus containing dendrimer with diphenylsilanediol as core unit.

A phosphorus containing dendrimer with a diphenylsilanediol core was synthesized using a divergent method. Several types of reactions were performed on dendrons of several sizes, either at the level of the core or the surface. The giant Schiff's base macro molecule possesses 12 imine bonds and 8 hydroxy groups on the terminal phenyl groups. The structures of the intermediate compounds were confirmed by IR, GCMS and ³¹P NMR. The final compound was characterized by ¹H, ¹³C, ³¹P NMR, MALDI-TOF MS and CHN analysis. Scanning electron microscopic and thermogravimetric analysis/differential scanning calorimetric studies were also performed on the final dendritic molecule.