On-Off Switching of Singlet Self-Trapped Exciton Emission Endows Antimony-Doped Indium Halides with Excitation-Wavelength-Dependent Luminescence.

Excitation-wavelength-dependent (Ex-De) emitters are a fascinating category of luminescent materials whose emission properties vary with the wavelength of the light used for excitation. Antimony (Sb)-doped indium (In)-based metal halides are efficient light emitters; however, the peak fluorescence emission of most Sb-activated In-halide remains independent of the excitation wavelength. Here, the study introduces a new Sb-doped In-halide cluster, (BDPA)InCl:Sb (BDPA = CHN, benzyldimethylphenylammonium), which demonstrates efficient Ex-De emission originating from the on-off switchable fluorescence behavior of singlet self-trapped exciton (STE) in 5-coordinate Sb dopant.

Excitation Wavelength-Dependent Fluorescence of a Lanthanide Organic Metal Halide Cluster for Anti-Counterfeiting Applications.

The achievement of significant photoluminescence (PL) in lanthanide ions (Ln ) has primarily relied on host sensitization, where energy is transferred from the excited host material to the Ln ions. However, this luminous mechanism involves only one optical antenna, namely the host material, which limits the accessibility of excitation wavelength-dependent (Ex-De) PL. Consequently, the wider application of Ln ions in light-emitting devices is hindered.

On the Mechanism of Solvents Catalyzed Structural Transformation in Metal Halide Perovskites.

Metal halide perovskites show the capability of performing structural transformation, allowing the formation of functional heterostructures. Unfortunately, the elusive mechanism governing these transformations limits their technological application. Herein, the mechanism of 2D-3D structural transformation is unraveled as catalyzed by solvents.

Structural Isomer of Fluorinated Ruddlesden-Popper Perovskites Toward Efficient and Stable 2D/3D Perovskite Solar Cells.

Defect passivation using two-dimensional (2D)-layered perovskites with organic spacers on 3D bulk perovskites has been proposed as an effective strategy to improve perovskite solar cell stability and efficiency. Specifically, fluorination of the organic spacers has been employed due to the resulting hydrophobic nature and the defect passivation characteristics. In addition to the type of functional groups attached to the spacer molecules, conformational changes of fluorine isomers on layered perovskites can provide an extended strategy to control a variety of opto-electrical properties related to the interlayer spacing.

Multifunctional Additive CdAc for Efficient Perovskite-Based Solar Cells.

Polycrystalline perovskite films fabricated on flexible and textured substrates often are highly defective, leading to poor performance of perovskite devices. Finding substrate-tolerant perovskite fabrication strategies is therefore paramount. Herein, this study shows that adding a small amount of Cadmium Acetate (CdAc ) in the PbI precursor solution results in nano-hole array films and improves the diffusion of organic salts in PbI and promotes favorable crystal orientation and suppresses non-radiative recombination.

Filling Chlorine Vacancy with Bromine: A Two-Step Hot-Injection Approach Achieving Defect-Free Hybrid Halogen Perovskite Nanocrystals.

Mixed-halide (Cl and Br) perovskite nanocrystals (NCs) are of particular interest because they hold great potential for use in high-efficiency blue light-emitting diodes (LEDs). Generally, mixed-halide compounds are obtained by either a one-step synthesis with simultaneous addition of both halide precursors or a postsynthetic anion exchange using the opposite halogen. However, both strategies fail to prevent the formation of deep-level Cl vacancy defects, rendering the photoluminescence quantum yields (PLQYs) typically lower than 30%.

Organic-Inorganic Hybrid Cuprous-Based Metal Halides for Warm White Light-Emitting Diodes.

Single-component emitters with stable and bright warm white-light emission are highly desirable for high-efficacy warm white light-emitting diodes (warm-WLEDs), however, materials with such luminescence properties are extremely rare. Low-dimensional lead (Pb) halide perovskites can achieve warm white photoluminescence (PL), yet they suffer from low stability and PL quantum yield (PLQY). While Pb-free air-stable perovskites such as Cs AgInCl emit desirable warm white light, sophisticated doping strategies are typically required to increase their PL intensity.

Germanium Halides Serving as Ideal Precursors: Designing a More Effective and Less Toxic Route to High-Optoelectronic-Quality Metal Halide Perovskite Nanocrystals.

The three-precursors approach has proven to be advantageous for obtaining high-quality metal halide perovskite nanocrystals (PNCs). However, the current halide precursors of choice are mainly limited to those highly toxic organohalides, being unfavorable for large-scale and sustainable use. Moreover, most of the resulting PNCs still suffer from low quality in terms of photoluminescence quantum yield (PLQY).

The role of sodium in stabilizing tin-lead (Sn-Pb) alloyed perovskite quantum dots.

Narrow-bandgap CsSn Pb I perovskite quantum dots (QDs) show great promise for optoelectronic applications owing to their reduced use of toxic Pb, improved phase stability, and tunable band gaps in the visible and near-infrared range. The use of small ions has been proven beneficial in enhancing the stability and photoluminescence quantum yield (PLQY) of perovskite QDs. The introduction of sodium (Na) has succeeded in boosting the PLQY of CsSnPbI QDs.

Stretchable AgX (X = Se, Te) for Efficient Thermoelectrics and Photovoltaics.

Transition metal chalcogenides (TMCs) have gained worldwide interest owing to their outstanding renewable energy conversion capability. However, the poor mechanical flexibility of most existing TMCs limits their practical commercial applications. Herein, triggered by the recent and imperative synthesis of highly ductile α-AgS, an effective approach based on evolutionary algorithm and ab initio total-energy calculations for determining stable, ductile phases of bulk and two-dimensional AgSe and AgTe compounds was implemented.

Near-Infrared Emission from Tin-Lead (Sn-Pb) Alloyed Perovskite Quantum Dots by Sodium Doping.

Phase-stable CsSn Pb I perovskite quantum dots (QDs) hold great promise for optoelectronic applications owing to their strong response in the near-infrared region. Unfortunately, optimal utilization of their potential is limited by the severe photoluminescence (PL) quenching, leading to extremely low quantum yields (QYs) of approximately 0.3 %.

Absolute energy level positions in tin- and lead-based halide perovskites.

Metal halide perovskites are promising materials for future optoelectronic applications. One intriguing property, important for many applications, is the tunability of the band gap via compositional engineering. While experimental reports on changes in absorption or photoluminescence show rather good agreement for different compounds, the physical origins of these changes, namely the variations in valence and conduction band positions, are not well characterized.

Stabilizing Lead-Free All-Inorganic Tin Halide Perovskites by Ion Exchange.

Because of its thermal stability, lead-free composition, and nearly ideal optical and electronic properties, the orthorhombic CsSnI perovskite is considered promising as a light absorber for lead-free all-inorganic perovskite solar cells. However, the susceptibility of this three-dimensional perovskite toward oxidation in air has limited the development of solar cells based on this material. Here, we report the findings of a computational study which identifies promising Rb Cs Sn(Br I ) perovskites for solar cell applications, prepared by substituting cations (Rb for Cs) and anions (Br for I) in CsSnI.

Exploration of new ferromagnetic, semiconducting and biocompatible NbX (X = Cl, Br or I) monolayers with considerable visible and infrared light absorption.

Ferromagnetic character and biocompatible properties have become key factors for developing next-generation spintronic devices and show potential in biomedical applications. Unfortunately, the Mn-containing monolayer is not biocompatible though it has been extensively studied, and the Cr-containing monolayer is not environmental friendly, although these monolayers are ferromagnetic. Herein, we systematically investigated new types of 2D ferromagnetic monolayers NbX (X = Cl, Br or I) by means of first principles calculations together with mean field approximation based on the classical Heisenberg model.

Tuning the electronic properties and work functions of graphane/fully hydrogenated h-BN heterobilayers via heteronuclear dihydrogen bonding and electric field control.

Using density functional theory calculations with van der Waals correction, we show that the electronic properties (band gap and carrier mobility) and work functions of graphane/fully hydrogenated hexagonal boron nitride (G/fHBN) heterobilayers can be favorably tuned via heteronuclear dihydrogen bonding (C-HH-B and C-HH-N) and an external electric field. Our results reveal that G/fHBN heterobilayers have different direct band gaps of ∼1.2 eV and ∼3.

Electronic structure and optical properties of graphene/stanene heterobilayer.

The structural, electronic and optical properties of the graphene hybrid with stanene, the tin counterpart of graphene, are investigated by means of density functional calculation with the observation of band gap opening and enhanced visible light response. The lattice mismatch between graphene and stanene is taken into consideration and several stacking methods for model construction are proposed to study the possible effects. The Dirac feature can be observed in this bilayer system with relatively stronger interlayer interaction than weak van der Waals forces, which is ascribed to the unsaturated p orbital of stanene.

Effect of multilayer structure, stacking order and external electric field on the electrical properties of few-layer boron-phosphide.

Development of nanoelectronics requires two-dimensional (2D) systems with both direct-bandgap and tunable electronic properties as they act in response to the external electric field (E-field). Here, we present a detailed theoretical investigation to predict the effect of atomic structure, stacking order and external electric field on the electrical properties of few-layer boron-phosphide (BP). We demonstrate that the splitting of bands and bandgap of BP depends on the number of layers and the stacking order.

Sorption and Diffusion of Water Vapor and Carbon Dioxide in Sulfonated Polyaniline as Chemical Sensing Materials.

A hybrid quantum mechanics (QM)/molecular dynamics (MD) simulation is performed to investigate the effect of an ionizable group (-SO₃(-)Na⁺) on polyaniline as gas sensing materials. Polymers considered for this work include emeraldine base of polyaniline (EB-PANI) and its derivatives (Na-SPANI (I), (II) and (III)) whose rings are partly monosubstituted by -SO₃(-)Na⁺. The hybrid simulation results show that the adsorption energy, Mulliken charge and band gap of analytes (CO₂ and H₂O) in polyaniline are relatively sensitive to the position and the amounts of -SO₃(-)Na⁺, and these parameters would affect the sensitivity of Na-SPANI/EB-PANI towards CO₂.