Grain engineering for efficient near-infrared perovskite light-emitting diodes.

Metal halide perovskites show promise for next-generation light-emitting diodes, particularly in the near-infrared range, where they outperform organic and quantum-dot counterparts. However, they still fall short of costly III-V semiconductor devices, which achieve external quantum efficiencies above 30% with high brightness. Among several factors, controlling grain growth and nanoscale morphology is crucial for further enhancing device performance.

The molecular epidemiology of respiratory syncytial virus in Ontario, Canada from 2022-2024 using a custom whole genome sequencing assay and analytics package.

Background: Respiratory Syncytial Virus (RSV) infections are a cause of significant morbidity and mortality in children and the elderly. Despite the clinical burden of disease, very little is known about the inter- and intra-seasonal genomic variability of RSV. Furthermore, the recent approval of vaccines and monoclonal antibody therapies will likely lead to higher selective pressure on RSV.

Correlating Halide Segregation with Photolysis in Mixed-Halide Perovskites via In situ Opto-gravimetric Analysis.

Halide oxidation plays a fundamental role in halide segregation and the degradation of halide perovskites, yet quantitative measurement of halide oxidation in solid-state perovskite samples remains challenging. Herein, we demonstrate that in situ opto-gravimetric measurements based on a quartz crystal microbalance can quantify the photolysis kinetics of solid-state perovskites. By investigating a series of mixed bromide/iodide perovskites with varying halide ratios, we demonstrate identical compositional thresholds ( ∼ 0.

Neurochemistry and functional connectivity in the brain of people with Charles Bonnet syndrome.

Background: Charles Bonnet syndrome (CBS) is a condition in which people with vision loss experience complex visual hallucinations. These complex visual hallucinations may be caused by increased excitability in the visual cortex that are present in some people with vision loss but not others.

Objectives: We aimed to evaluate the association between γ-aminobutyric acid (GABA) in the visual cortex and CBS.

Halide Perovskite Thin Film Lasing Mode Control.

Metal halide perovskite semiconductors have emerged as highly efficient amplifying materials; to ensure practical applicability, it is important to have precise control over the spectral and polarization characteristics of lasing emission. In this study, we present effective strategies for manipulating single- and multimode lasing from surface-emitting and optically pumped perovskite distributed feedback lasers. We show that cladding structures can be made to modify the optical properties of guided transverse electric and magnetic modes within the gain medium.

Discovery of Crystallizable Organic Semiconductors with Machine Learning.

Crystalline organic semiconductors are known to have improved charge carrier mobility and exciton diffusion length in comparison to their amorphous counterparts. Certain organic molecular thin films can be transitioned from initially prepared amorphous layers to large-scale crystalline films via abrupt thermal annealing. Ideally, these films crystallize as platelets with long-range-ordered domains on the scale of tens to hundreds of microns.

A General Approach to Activate Second-Scale Room Temperature Photoluminescence in Organic Small Molecules.

Organic small molecules that exhibit second-scale phosphorescence at room temperature are of interest for potential applications in sensing, anticounterfeiting, and bioimaging. However, such materials systems are uncommon-requiring millisecond to second-scale triplet lifetimes, efficient intersystem crossing, and slow rates of nonradiative recombination. Here, a simple and scalable approach is demonstrated to activate long-lived phosphorescence in a wide variety of molecules by suspending them in rigid polymer hosts and annealing them above the polymer's glass transition temperature.

Sublimed C for efficient and repeatable perovskite-based solar cells.

Thermally evaporated C is a near-ubiquitous electron transport layer in state-of-the-art p-i-n perovskite-based solar cells. As perovskite photovoltaic technologies are moving toward industrialization, batch-to-batch reproducibility of device performances becomes crucial. Here, we show that commercial as-received (99.

Substrate-embedded metal meshes for ITO-free organic light emitting diodes.

Organic light-emitting diodes (OLEDs) have great potential for use in large-area display and lighting applications, but their widespread adoption for large areas is hindered by the high cost and insufficient performance of indium tin oxide (ITO) anodes. In this study, we introduce an alternative anode material - a silver mesh embedded in glass - to facilitate production of large-area OLEDs. We present a facile, scalable manufacturing technique to create high aspect ratio micromeshes embedded in glass to provide the planar geometry needed for OLED layers.

Thin-Film Organic Heteroepitaxy.

Incorporating crystalline organic semiconductors into electronic devices requires understanding of heteroepitaxy given the ubiquity of heterojunctions in these devices. However, while rules for commensurate epitaxy of covalent or ionic inorganic material systems are known to be dictated by lattice matching constraints, rules for heteroepitaxy of molecular systems are still being written. Here, it is found that lattice matching alone is insufficient to achieve heteroepitaxy in molecular systems, owing to weak intermolecular forces that describe molecular crystals.

Triiodide Attacks the Organic Cation in Hybrid Lead Halide Perovskites: Mechanism and Suppression.

Molecular I can be produced from iodide-based lead perovskites under thermal stress; triiodide, I , is formed from this I and I . Triiodide attacks protic cation MA - or FA -based lead halide perovskites (MA , methylammonium; FA , formamidinium) as explicated through solution-based nuclear magnetic resonance (NMR) studies: triiodide has strong hydrogen-bonding affinity for MA or FA , which leads to their deprotonation and perovskite decomposition. Triiodide is a catalyst for this decomposition that can be obviated through perovskite surface treatment with thiol reducing agents.

Thermal Properties of Polymer Hole-Transport Layers Influence the Efficiency Roll-off and Stability of Perovskite Light-Emitting Diodes.

While the performance of metal halide perovskite light-emitting diodes (PeLEDs) has rapidly improved in recent years, their stability remains a bottleneck to commercial realization. Here, we show that the thermal stability of polymer hole-transport layers (HTLs) used in PeLEDs represents an important factor influencing the external quantum efficiency (EQE) roll-off and device lifetime. We demonstrate a reduced EQE roll-off, a higher breakdown current density of approximately 6 A cm, a maximum radiance of 760 W sr m, and a longer device lifetime for PeLEDs using polymer HTLs with high glass-transition temperatures.

Toward Nonepitaxial Laser Diodes.

Thin-film organic, colloidal quantum dot, and metal halide perovskite semiconductors are all being pursued in the quest for a wavelength-tunable diode laser technology that does not require epitaxial growth on a traditional semiconductor substrate. Despite promising demonstrations of efficient light-emitting diodes and low-threshold optically pumped lasing in each case, there are still fundamental and practical barriers that must be overcome to reliably achieve injection lasing. This review outlines the historical development and recent advances of each material system on the path to a diode laser.

Origins of Photoluminescence Instabilities at Halide Perovskite/Organic Hole Transport Layer Interfaces.

Metal halide perovskites are promising for optoelectronic device applications; however, their poor stability under solar illumination remains a primary concern. While the intrinsic photostability of isolated neat perovskite samples has been widely discussed, it is important to explore how charge transport layers─employed in most devices─impact photostability. Herein, we study the effect of organic hole transport layers (HTLs) on light-induced halide segregation and photoluminescence (PL) quenching at perovskite/organic HTL interfaces.

Electrochemical Doping of Halide Perovskites by Noble Metal Interstitial Cations.

Metal halide perovskites are an attractive class of semiconductors, but it has proven difficult to control their electronic doping by conventional strategies due to screening and compensation by mobile ions or ionic defects. Noble-metal interstitials represent an under-studied class of extrinsic defects that plausibly influence many perovskite-based devices. In this work, doping of metal halide perovskites is studied by electrochemically formed Au interstitial ions, combining experimental data on devices with a computational analysis of Au interstitial defects based on density functional theory (DFT).

Individual-level determinants of COVID-19 vaccination in pregnant people in East Tennessee.

Objective: Coronavirus disease 2019 (COVID-19) infection during pregnancy increases the risk of severe illness and death. This study describes individual-level determinants of COVID-19 vaccination among pregnant people in East Tennessee.

Methods: Advertisements for the online Moms and Vaccines survey were placed in prenatal clinics in Knoxville, Tennessee.

A comprehensive picture of roughness evolution in organic crystalline growth: the role of molecular aspect ratio.

Exploiting the capabilities of organic semiconductors for applications ranging from light-emitting diodes to photovoltaics to lasers relies on the creation of ordered, smooth layers for optimal charge carrier mobilities and exciton diffusion. This, in turn, creates a demand for organic small molecules that can form smooth thin film crystals homoepitaxy. We have studied a set of small-molecule organic semiconductors that serve as templates for homoepitaxy.

Hot-Casting-Assisted Liquid Additive Engineering for Efficient and Stable Perovskite Solar Cells.

High-performance inorganic-organic lead halide perovskite solar cells (PSCs) are often fabricated with a liquid additive such as dimethyl sulfoxide (DMSO), which retards crystallization and reduces roughness and pinholes in the perovskite layers. However, DMSO can be trapped during perovskite film formation and induce voids and undesired reaction byproducts upon later processing steps. Here, it is shown that the amount of residual DMSO can be reduced in as-spin-coated films significantly through use of preheated substrates, or a so-called hot-casting method.

Untying the Cesium "Not": Cesium-Iodoplumbate Complexation in Perovskite Solution-Processing Inks Has Implications for Crystallization.

We illustrate the critical importance of the energetics of cation-solvent versus cation-iodoplumbate interactions in determining the stability of ABX perovskite precursors in a dimethylformamide (DMF) solvent medium. We have shown, through a complementary suite of nuclear magnetic resonance (NMR) and computational studies, that Cs exhibits significantly different solvent vs iodoplumbate interactions compared to organic A-site cations such as CHNH (MA). Two NMR studies were conducted: Cs NMR analysis shows that Cs and MA compete for coordination with PbI in DMF.

Diabetes risk status and meeting the US physical activity recommendations in reproductive-aged women: 2011, 2013, 2015 and 2017 Behavioral Risk Factor Surveillance System.

Background: Women at increased risk for type 2 diabetes, due to recognized prediabetes (PD) or previous gestational diabetes (GD), stand to benefit from meeting U.S. physical activity (PA) recommendations.

Improved Charge Balance in Green Perovskite Light-Emitting Diodes with Atomic-Layer-Deposited AlO.

Perovskite light-emitting diodes (LEDs) have experienced a rapid increase in efficiency over the last several years and are now regarded as promising low-cost devices for displays and communication systems. However, it is often challenging to employ ZnO, a well-studied electron transport material, in perovskite LEDs due to chemical instability at the ZnO/perovskite interface and charge injection imbalance caused by the relatively high conductivity of ZnO. In this work, we address these problems by depositing an ultrathin AlO interlayer at the ZnO/perovskite interface, allowing the fabrication of green-emitting perovskite LEDs with a maximum luminance of 21 815 cd/m.

Powerful Organic Molecular Oxidants and Reductants Enable Ambipolar Injection in a Large-Gap Organic Homojunction Diode.

Doping has proven to be a critical tool for enhancing the performance of organic semiconductors in devices like organic light-emitting diodes. However, the challenge in working with high-ionization-energy (IE) organic semiconductors is to find p-dopants with correspondingly high electron affinity (EA) that will improve the conductivity and charge carrier transport in a film. Here, we use an oxidant that has been recently recognized to be a very strong p-type dopant, hexacyano-1,2,3-trimethylene-cyclopropane (CN6-CP).