Light-Triggered Reversible Assembly of Halide Perovskite Nanoplatelets.

Advancements in stimuli-driven nanoactuators necessitate the discovery of photo-switchable, self-contained semiconductor nanostructures capable of precise mechanical responses. The reversible assembly of 0D CsBiI halide perovskite nanoplatelets (NPLs) between stacked and scattered configurations are demonstrated under light and dark, respectively. This sunlight-triggered perpetual flipping of the NPLs, occurring in less than a minute, is associated with a color change between brown and red.

Footprints of scanning probe microscopy on halide perovskites.

Scanning probe microscopy (SPM) and advanced atomic force microscopy (AFM) have become pivotal for nanoscale elucidation of the structural, optoelectronic and photovoltaic properties of halide perovskite single crystals and polycrystalline films, both under and conditions. These techniques reveal detailed information about film topography, compositional mapping, charge distribution, near-field electrical behaviors, cation-lattice interactions, ion dynamics, piezoelectric characteristics, mechanical durability, thermal conductivity, and magnetic properties of doped perovskite lattices. This article outlines the advancements in SPM techniques that deepen our understanding of the optoelectronic and photovoltaic performances of halide perovskites.

Visible-Light Photodetection by Zero-Dimensional Hybrid Indium-Halide with Minimal Structural Distortion and Reduced Band Gap.

Perovskite-inspired zero-dimensional (0D) hybrid halides exhibit impressive light emission properties; however, their potential in photovoltaics is hindered by the absence of interconnection between the inorganic polyhedra, leading to acute radiative recombination and insufficient charge separation. We demonstrate that incorporating closely-spaced dissimilar polyhedral units with minimal structural distortion leads to a remarkable enhancement in visible-light photodetection capability. We designed 0D CHNInBr (HIB) with a tetragonal crystal system, replacing the Cs of CsInBr.

Optoelectronic insights of lead-free layered halide perovskites.

Two-dimensional organic-inorganic halide perovskites have emerged as promising candidates for a multitude of optoelectronic technologies, owing to their versatile structure and electronic properties. The optical and electronic properties are harmoniously integrated with both the inorganic metal halide octahedral slab, and the organic spacer layer. The inorganic octahedral layers can also assemble into periodically stacked nanoplatelets, which are interconnected by the organic ammonium cation, resulting in the formation of a superlattice or superstructure.

Hydrogen Evolution in Neutral Media by Differential Intermediate Binding at Charge-Modulated Sites of a Bimetallic Alloy Electrocatalyst.

The energy barrier to dissociate neutral water has been lowered by the differential intermediate binding on the charge-modulated metal centers of CoMo sheets supported on Ni-foam (NF), where the overpotential for hydrogen evolution reaction (HER) in 1 M phosphate buffer solution (PBS) is only 50±9 mV at -10 mA cm. It has a turnover frequency (TOF) of 0.18 s, mass activity of 13.

Facet-specific ligand dynamics: scaling the descriptors of CsAgBiBr nanocrystals.

Facet control by primary amines can bolster the optoelectronic parameters of ABB'X perovskite nanocrystals (NCs) with large indirect bandgaps. The 18-C amine competitively attaches to the (222) facet of CsAgBiBr (CABB) NCs, 16-C and 14-C bind to (400) and (440), and 12-C binds to (400). The NCs with only the (400) facet decrease the bandgap and exciton binding energy by 0.

Spin Texture Sensitive Photodetection by Dion-Jacobson Tin Halide Perovskites.

The organic spacer molecule is known to regulate the optoelectronic properties of two-dimensional (2D) perovskites. We show that the spacer layer thickness determines the nature of optical transitions, direct or indirect, by controlling the structural properties of the inorganic layer. The spin-orbit interactions lead to different electron spin orientations for the states associated with the conduction band minimum (CBM) and the valence band maximum (VBM).

Positive Feedback Mechanism of Probe Sonication for the Perovskite Films in Solar Cells.

The performance of perovskite solar cells (PSCs) is governed by the quality of perovskite films, whereby compact, pinhole-free perovskite films are desired, in addition to its composition. We have demonstrated probe sonication as a processing technique to provide positive feedback for enhancing the perovskite film quality and photovoltaic parameters, with two systems, CHNHPbI (MAPbI) and CsFAPb(IBr). In probe sonication, the ultrasound results in the formation, growth, and collapse of the bubbles through shock wave inside the gas phase of the collapsing bubble.

Nanoplatelet Superlattices by Tin-Induced Transformation of FAPbI Nanocrystals.

The transition from 3D to 2D lead halide perovskites is traditionally led by the lattice incorporation of bulky organic cations. However, the transformation into a coveted 2D superlattice-like structure by cationic substitution at the Pb site of 3D perovskite is unfamiliar. It is demonstrated that the gradual increment of [Sn ] alters the FASn Pb I nanocrystals into the Ruddlesden-Popper-like nanoplatelets (NPLs), with surface-absorbed oleic acid (OA) and oleylamine (OAm) spacer ligand at 80 °C (FA : formamidinium cation).

Transition from Dion-Jacobson hybrid layered double perovskites to 1D perovskites for ultraviolet to visible photodetection.

New perovskite phases having diverse optoelectronic properties are the need of the hour. We present five variations of RAgM(iii)X, where R = NHCHNH (4N4) or NHCHNH (6N6); M(iii) = Bi or Sb; and X = Br or I, by tuning the composition of (4N4)AgBiBr, a structurally rich hybrid layered double perovskite (HLDP). (4N4)AgBiBr, (4N4)AgSbBr, and (6N6)AgBiBr crystallize as Dion-Jacobson (DJ) HLDPs, whereas 1D (6N6)SbBr, (4N4)-BiI and (4N4)-SbI have -connected chains by corner-shared octahedra.

Multimodal Biofilm Inactivation Using a Photocatalytic Bismuth Perovskite-TiO-Ru(II)polypyridyl-Based Multisite Heterojunction.

Infectious bacterial biofilms are recalcitrant to most antibiotics compared to their planktonic version, and the lack of appropriate therapeutic strategies for mitigating them poses a serious threat to clinical treatment. A ternary heterojunction material derived from a Bi-based perovskite-TiO hybrid and a [Ru(2,2'-bpy)(4,4'-dicarboxy-2,2'-bpy)] (2,2'-bpy, 2,2'-bipyridyl) as a photosensitizer (RuPS) is developed. This hybrid material is found to be capable of generating reactive oxygen species (ROS)/reactive nitrogen species (RNS) upon solar light irradiation.

Inverse 'intra-lattice' charge transfer in nickel-molybdenum dual electrocatalysts regulated by under-coordinating the molybdenum center.

The prevalence of intermetallic charge transfer is a marvel for fine-tuning the electronic structure of active centers in electrocatalysts. Although Pauling electronegativity is the primary deciding factor for the direction of charge transfer, we report an unorthodox intra-lattice 'inverse' charge transfer from Mo to Ni in two systems, NiMo alloy electrodeposited on Cu nanowires and NiMo-hydroxide (Ni : Mo = 5 : 1) on Ni foam. The inverse charge transfer deciphered by X-ray absorption fine structure studies and X-ray photoelectron spectroscopy has been understood by the Bader charge and projected density of state analyses.

Lattice Mismatch Guided Nickel-Indium Heterogeneous Alloy Electrocatalysts for Promoting the Alkaline Hydrogen Evolution.

The immiscibility of crystallographic facets in multi-metallic catalysts plays a key role in driving the green H production by water electrolysis. The lattice mismatch between tetragonal In and face-centered cubic (fcc) Ni is 14.9 % but the mismatch with hexagonal close-packed (hcp) Ni is 49.

Covalent Organic Framework Thin-Film Photodetectors from Solution-Processable Porous Nanospheres.

The synthesis of homogeneous covalent organic framework (COF) thin films on a desired substrate with decent crystallinity, porosity, and uniform thickness has great potential for optoelectronic applications. We have used a solution-processable sphere transmutation process to synthesize 300 ± 20 nm uniform COF thin films on a 2 × 2 cm TiO-coated fluorine-doped tin oxide (FTO) surface. This process controls the nucleation of COF crystallites and molecular morphology that helps the nanospheres to arrange periodically to form homogeneous COF thin films.

Spacer Switched Two-Dimensional Tin Bromide Perovskites Leading to Ambient-Stable Near-Unity Photoluminescence Quantum Yield.

Semiconductor nanostructures with near-unity photoluminescence quantum yields (PLQYs) are imperative for light-emitting diodes and display devices. A PLQY of 99.7 ± 0.

4nπ Stable Multitasking Azapentacene: Acidochromism, Hole Mobility, and Visible Light Photoresponse.

Herein, we describe the synthesis, characterization, and optoelectronic investigation of a stable 4nπ dihydrotetraazapentacene derivative. The neutral dihydrotetraazapentacene contains a 24π-conjugated -heteroacene core with two phenyl pendants appended thereof. The exceptional stability of this formally antiaromatic π-system is attributed to the fused dihydropyrazine ring, which has ethenamine (enamine) conjugations, and hence, the π-electrons delocalize over the nearly planar azapentacene core to endow with a global aromatic characteristic.

CsCuSbClI( = 0-10) nanocrystals for visible light photodetection.

Lead-free layered double perovskite nanocrystals (NCs) with tunable visible range emission, high carrier mobility and low trap density are the need of the hour to make them applicable for optoelectronic and photovoltaic devices. Introduction of Cuin the high band gap CsSbCllattice transforms it to the monoclinic CsCuSbCl(CCSC) NCs having a direct band gap of 1.96 eV.

The Perfect Imperfections in Electrocatalysts.

Modern day electrochemical devices find applications in a wide range of industrial sectors, from consumer electronics, renewable energy management to pollution control by electric vehicles and reduction of greenhouse gas. There has been a surge of diverse electrochemical systems which are to be scaled up from the lab-scale to industry sectors. To achieve the targets, the electrocatalysts are continuously upgraded to meet the required device efficiency at a low cost, increased lifetime and performance.

CsBiI nanodiscs with phase and Bi(III) state stability under reductive potential or illumination for H generation from diluted aqueous HI.

The increasingly popular, lead-free perovskite, CsBiI has a vulnerable Bi state under reductive potentials, due to the high standard reduction potential of Bi/Bi (0 < < 3). Contrary to this fundamental understanding, herein, ligand-coated CsBiI nanodiscs (NDs) demonstrate outstanding electrochemical stability with up to -1 V a saturated calomel electrode in aqueous 0.63 M (5% v/v) and 6.

Photodetectors with High Responsivity by Thickness Tunable Mixed Halide Perovskite Nanosheets.

Chemical transformation of typically "nonlayered" phases into two-dimensional structures remains a formidable task. Among the thickness tunable CsPbX ( = Br, Br/I, I) nanosheets (NSs), CsPbBrI NSs with a thickness of ∼4.9 nm have structural stability superior to ∼6.

Comprehensive and High-throughput Electrolysis of Water and Urea by 3-5 nm Nickel and Copper Coordination Polymers.

Metal-organic coordination polymers (CP) have attracted the scientific attention for electrochemical water oxidation as it has the similar coordination structure like natural photosynthetic coordinated complex. However, the harsh synthesis conditions and bulky nature pose a major challenge in the field of catalysis. Herein, 3-5 nm CP particles synthesized at room temperature using aqueous solutions of Ni /Cu and 2,5-dihydroxyterepthalic acid as precursor were applied for alkaline water and urea electrolysis.

An electrochemically reversible lattice with redox active A-sites of double perovskite oxide nanosheets to reinforce oxygen electrocatalysis.

The catalyst surface undergoes reversible structural changes while influencing the rate of redox reactions, the atomistic structural details of which are often overlooked when the key focus is to enhance the catalytic activity and reaction yield. We achieve chemical synthesis of ∼5 unit cell thick double perovskite oxide nanosheets (NSs) and demonstrate their precise structural reversibility while catalyzing the successive oxygen evolution and reduction reactions (OER/ORR). 4.

An unconventional route to an ambipolar azaheterocycle and its generated radical anion.

Herein we report the synthesis, characterization and application of an azaheterocycle 4 obtained via an unprecedented C-N coupling. The neutral azaheterocycle undergoes one-electron reduction to form an air-stable radical anion in situ, which provides added benefit towards operational stability of the device during n-type charge transport. The unusual stability of this radical anion is due to the fact that the fused cyclopentane ring upon reduction forms aromatic cyclopentadienyl anion, and the negative charge delocalizes over the nearly planar azaheterocycle core.

Unraveling the Charge Transport Mechanism in Mechanochemically Processed Hybrid Perovskite Solar Cell.

The long-term operation of organic-inorganic hybrid perovskite solar cells is hampered by the microscopic strain introduced by the multiple thermal cycles during the synthesis of the material via a solution process route. This setback can be eliminated by a room temperature synthesis scheme. In this work, a mechanochemical synthesis technique at room temperature is employed to process CHNHPbIBr films for fabricating perovskite solar cell devices.

In Situ Cation Intercalation in the Interlayer of Tungsten Sulfide with Overlaying Layered Double Hydroxide in a 2D Heterostructure for Facile Electrochemical Redox Activity.

The role of electrochemical interfaces in energy conversion and storage is unprecedented and more so the interlayers of two-dimensional (2D) heterostructures, where the physicochemical nature of these interlayers can be adjusted by cation intercalation. We demonstrate intercalation of Ni and Co with similar ionic radii of ∼0.07 nm in the interlayer of 1T-WS while electrodepositing NiCo layered double hydroxide (NiCo-LDH) to create a 2D heterostructure.