Efficient Ruddlesden-Popper Perovskite Light-Emitting Diodes with Randomly Oriented Nanocrystals

Ruddlesden-Popper phase (RP-phase) perovskites that consist of 2D perovskite slabs interleaved with bulky organic ammonium (OA) are favorable for light-emitting diodes (LEDs). The critical limitation of LED applications is that the insulating OA arranged in a preferred orientation limits charge transport. Therefore, the ideal solution is to achieve a randomly connected structure that can improve charge transport without hampering the confinement of the electron-hole pair. Here, a structurally modulated RP-phase metal halide perovskite (MHP), (PEA)(2)(CH3NH3)(m-1)PbmBr3m+1 is introduced to make the randomly oriented RP-phase unit and ensure good connection between them by applying modified nanocrystal pinning, which leads to an increase in the efficiency of perovskite LEDs (PeLEDs). The randomly connected RP-phase MHP forces contact between inorganic layers and thereby yields efficient charge transport and radiative recombination. Combined with an optimal dimensionality, (PEA)(2)(CH3NH3)(2)Pb3Br10, the structurally modulated RP-phase MHP exhibits increased photoluminescence quantum efficiency, from 0.35% to 30.3%, and their PeLEDs show a 2,018 times higher current efficiency (20.18 cd A(-1)) than in the 2D PeLED (0.01 cd A(-1)) and 673 times than in the 3D PeLED (0.03 cd A(-1)) using the same film formation process. This approach provides insight on how to solve the limitation of RP-phase MHP for efficient PeLEDs.

Synthesis and characterization of new silver(I) naphthalenedisulfonate complexes with heterocyclic N-donor ligands: Packing analyses and antibacterial studies

Four new silver(I) naphthalenedisulphonate complexes, [Ag 2 (1,5-nds) (β-Pic) 4 ]·2H 2 O (1), [Ag 2 (1,5-nds)(γ-Pic) 4 ]·6H 2 O (2), [Ag 2 (2,6-nds) (β-Pic) 4 ] (3) and [Ag 2 (2,6-nds) (γ-Pic) 4 ]·2H 2 O (4) have been synthesized using appropriate starting materials at ambient temperature and normal reaction conditions and fully characterized by spectroscopic methods (FT-IR, NMR). The structures of all the four complexes were determined using single crystal X-ray diffraction techniques and a detailed analysis of the role of weak non-covalent interactions in the solid state (hydrogen bonds, argentophylic interactions, π⋯π interactions) were investigated. Antibacterial activities of all complexes have been evaluated, indicating their high efficacy against both gram positive and gram negative bacterial strains

In situ studies of strain dependent transport properties of conducting polymers on elastomeric substrates

We report the changes in the surface electrical resistance, R, of conducting polymer, Poly(3,4- ethylenedioxythiophene)- poly(styrenesulfonate) (PEDOT:PSS) films coated on appropriate flexible substrates in stretched conditions. These studies are important in the context of flexible organic electronic applications. In situ conductivity measurements on pristine PEDOT:PSS thin films on elastomeric substrates upon stretching reveal a minima in R as a function of strain, x, prior to the expected increase at higher strain levels. The studies emphasize (i) role of substrates, (ii) stress- induced anisotropic features, and temperature dependence of R (iii) in comparison of R(x) in polymer films to that of conventional metal films. The stress induced changes is modeled in terms of effective medium approximation

Research Data Supporting "Slow Carrier Cooling in Hybrid Pb-Sn Halide Perovskites"

This data is from the Rao group in the Optoelectronics Group at the Cavendish Laboratory. The pump-probe spectra for CH3NH3Pb1-xSnxI3 are collected on a home-built pump-probe spectrometer. Data measurement and collection are done with LabVIEW routines. Data processing is performed in MATLAB R2018b. Analysis of the spectra is performed in Origin Pro 2017 64 bit. Figures for publication are arranged in Inkscape 0.92.4

Facile Fabrication of Ultra-Stretchable Metallic Nanocluster Films for Wearable Electronics

With recent progress in flexible electronics, developing facile one-step techniques for fabricating stretchable conductors and interconnects remain essential. It is also desirable for these processes to have a small number of processing steps, incorporate micropatterning, and be capable of being effortlessly implemented for manufacturing of wearable logic circuits. A low vacuum flash evaporation of Au nanoclusters is proposed as a facile method to fabricate highly stretchable conductors capable of fulfilling all such requirements. High metal-elastomer adhesion on textured substrates ensures low surface resistances (100% strain ≈ 25 Ω-sq^–1) where thin film Au accommodate strain like a “bellow”. Stretchability for conductors deposited on non-prestretched textured substrates up to 150% and smooth PDMS substrates up to 200% are shown. The system is modeled on a microscopic system calculating 2-D current continuity equations. Devising low cost techniques for fabricating stretchable conductors remains essential and in that direction stretchable circuits, heating elements have been demonstrated

Effect of heterocyclic nitrogen donor ligands on coordination behavior of weakly coordinating arylsulfonate: Synthesis, characterization and antimicrobial activities of [Cu(β-pic)4(2-Cl-5-nitrobenzenesulfonate)2](methanol) and [Cu(γ-pic)4(2-Cl-5 nitrobenzenesulfonate)2]

Two new copper(II) complexes [Cu(β-pic)4(2-Cl-5-nitrobenzenesulfonate)2](CH3OH) (1) and [Cu(γ-pic)4(2-Cl-5-nitrobenzenesulfonate)2] (2) have been synthesized by reacting appropriate starting materials in methanol:water (v/v 4:1). Both newly synthesized complexes have been characterized on the basis of elemental analyses, spectroscopic techniques (FT-IR, UV–Vis, EPR) and single crystal X-ray structure determination (complex 1). The structural analysis of complex 1 revealed the existence of unusual coordination behavior of arylsulfonate towards copper(II) center in presence of heterocyclic N-donor ligands resulting in elongated octahedral geometry around the metal. The EPR spectroscopy of complexes 1 and 2 unambiguously proved a similar coordination of four picolines in Cu(II) xy plane. Antimicrobial studies of both the complexes 1 and 2 were performed against Gram positive, MRSA (Methicillin-Resistant Staphylococcus aureus) as well as Gram negative (Escherichia coli, Klebsiella pneumoniae) bacteria. The activity was investigated by using both Agar well diffusion as well as MIC assay. Both the complexes show significant bactericidal activity against all the pathogenic strains in comparison to ampicillin, a broad spectrum antibiotic against Gram positive and Gram negative bacteria

Hybrid inorganic-organic complexes: Synthesis, spectroscopic characterization, single crystal X-ray structure determination and antimicrobial activities of three copper(II)-diethylenetriamine-p-nitrobenzoate complexes

Three new hybrid inorganic-organic complexes: [Cu(dien)(pnb)2]·H2O, 1; [Cu(dien)2](pnb)2, 2; and [Cu(dien)(pnb)(H2O)](pnb)(Hpnb), 3 (where pnb = p-nitrobenzoate, dien = diethylenetriamine, tridenate N-donor ligand), have been synthesized at room temperature and characterized by spectroscopic (FT-IR, UVâ\u80\u93Vis, EPR) methods. The structures of all newly synthesized complexes 1â\u80\u933 have been unambiguously established by single crystal X-ray structure determination. All the complexes 1â\u80\u933 showed variation in the coordination environment around copper(II) metal center obtained under slightly different reaction conditions by using same reactants but different synthetic routes at room temperature. Crystal lattices of coordination complexes 1â\u80\u933 are stabilized by various non-covalent interactions such as N-Hâ\u80¦O, C-Hâ\u80¦O, O-Hâ\u80¦O etc. All the three copper(II) complexes 1â\u80\u933 show significant antimicrobial activity against gram positive bacteria

Efficient Ruddlesden–Popper Perovskite Light‐Emitting Diodes with Randomly Oriented Nanocrystals

Ruddlesden-Popper phase (RP-phase) perovskites that consist of 2D perovskite slabs interleaved with bulky organic ammonium (OA) are favorable for light-emitting diodes (LEDs). The critical limitation of LED applications is that the insulating OA arranged in a preferred orientation limits charge transport. Therefore, the ideal solution is to achieve a randomly connected structure that can improve charge transport without hampering the confinement of the electron-hole pair. Here, a structurally modulated RP-phase metal halide perovskite (MHP), (PEA)(2)(CH3NH3)(m-1)PbmBr3m+1 is introduced to make the randomly oriented RP-phase unit and ensure good connection between them by applying modified nanocrystal pinning, which leads to an increase in the efficiency of perovskite LEDs (PeLEDs). The randomly connected RP-phase MHP forces contact between inorganic layers and thereby yields efficient charge transport and radiative recombination. Combined with an optimal dimensionality, (PEA)(2)(CH3NH3)(2)Pb3Br10, the structurally modulated RP-phase MHP exhibits increased photoluminescence quantum efficiency, from 0.35% to 30.3%, and their PeLEDs show a 2,018 times higher current efficiency (20.18 cd A(-1)) than in the 2D PeLED (0.01 cd A(-1)) and 673 times than in the 3D PeLED (0.03 cd A(-1)) using the same film formation process. This approach provides insight on how to solve the limitation of RP-phase MHP for efficient PeLEDs.N