Autonomous nanomanufacturing of lead-free metal halide perovskite nanocrystals using a self-driving fluidic lab.

Lead-based metal halide perovskite (MHP) nanocrystals (NCs) have emerged as a promising class of semiconducting nanomaterials for a wide range of optoelectronic and photoelectronic applications. However, the intrinsic lead toxicity of MHP NCs has significantly hampered their large-scale device applications. Copper-base MHP NCs with composition-tunable optical properties have emerged as a prominent lead-free MHP NC candidate.

Inverse Growth of Large-Grain-Size and Stable Inorganic Perovskite Micronanowire Photodetectors.

Control of forward and inverse reactions between perovskites and precursor materials is key to attaining high-quality perovskite materials. Many techniques focus on synthesizing nanostructured CsPbX materials (e.g.

Imaging of the Atomic Structure of All-Inorganic Halide Perovskites.

All-inorganic halide perovskites are promising materials for optoelectronic applications. The surface or interface structure of the perovskites plays a crucial role in determining the optoelectronic conversion efficiency, as well as the material stability. A thorough understanding of surface atomic structures of the inorganic perovskites and their contributions to their optoelectronic properties and stability is lacking.

Water Splitting Exceeding 17% Solar-to-Hydrogen Conversion Efficiency Using Solution-Processed Ni-Based Electrocatalysts and Perovskite/Si Tandem Solar Cell.

Various noble metal-free electrocatalysts have been explored to enhance the overall water splitting efficiency. Ni-based compounds have attracted substantial attention for achieving efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts. Here, we show superior electrocatalysts based on NiFe alloy electroformed by a roll-to-roll process.

Unraveling the Impact of Halide Mixing on Perovskite Stability.

Increasing the stability of perovskites is essential for their integration in commercial photovoltaic devices. Halide mixing is suggested as a powerful strategy toward stable perovskite materials. However, the stabilizing effect of the halides critically depends on their distribution in the mixed compound, a topic that is currently under intense debate.

Universal Approach toward Hysteresis-Free Perovskite Solar Cell via Defect Engineering.

Organic-inorganic halide perovskite is believed to be a potential candidate for high efficiency solar cells because power conversion efficiency (PCE) was certified to be more than 22%. Nevertheless, mismatch of PCE due to current density (J)-voltage (V) hysteresis in perovskite solar cells is an obstacle to overcome. There has been much lively debate on the origin of J-V hysteresis; however, effective methodology to solve the hysteric problem has not been developed.

Printable organometallic perovskite enables large-area, low-dose X-ray imaging.

Medical X-ray imaging procedures require digital flat detectors operating at low doses to reduce radiation health risks. Solution-processed organic-inorganic hybrid perovskites have characteristics that make them good candidates for the photoconductive layer of such sensitive detectors. However, such detectors have not yet been built on thin-film transistor arrays because it has been difficult to prepare thick perovskite films (more than a few hundred micrometres) over large areas (a detector is typically 50 centimetres by 50 centimetres).

Interfacial Modification of Perovskite Solar Cells Using an Ultrathin MAI Layer Leads to Enhanced Energy Level Alignment, Efficiencies, and Reproducibility.

For the first time, we intentionally deposit an ultrathin layer of excess methylammonium iodide (MAI) on top of a methylammonium lead iodide (MAPI) perovskite film. Using photoelectron spectroscopy, we investigate the role of excess MAI at the interface between perovskite and spiro-MeOTAD hole-transport layer in standard structure perovskite solar cells (PSCs). We found that interfacial, favorable, energy-level tuning of the MAPI film can be achieved by controlling the amount of excess MAI on top of the MAPI film.

Initial Pattern of Optic Nerve Enhancement in Korean Patients with Unilateral Optic Neuritis.

Purpose: The purpose of this study was to demonstrate whether the pattern of optic nerve enhancement in magnetic resonance imaging (MRI) can help to differentiate between idiopathic optic neuritis (ON), neuromyelitis optica (NMO), and multiple sclerosis (MS) in unilateral ON.

Methods: An MRI of the brain and orbits was obtained in patients with acute unilateral ON. Patients with ON were divided into three groups: NMO, MS, and idiopathic ON.

RISK FACTORS AND CLINICAL SIGNIFICANCE OF PRECHOROIDAL CLEFT IN NEOVASCULAR AGE-RELATED MACULAR DEGENERATION.

Purpose: To investigate the risk factors associated with prechoroidal cleft occurrence after treatment for neovascular age-related macular degeneration (nAMD) and to elucidate its clinical significance.

Methods: Two hundred thirty-four subjects who were treated for neovascular age-related macular degeneration were assessed to identify prechoroidal cleft on optical coherence tomography. Clinical variables were compared between patients manifesting a cleft (cleft group) and patients who did not (control group).

Observation of Enhanced Hole Extraction in Br Concentration Gradient Perovskite Materials.

Enhancing hole extraction inside the perovskite layer is the key factor for boosting photovoltaic performance. Realization of halide concentration gradient perovskite materials has been expected to exhibit rapid hole extraction due to the precise bandgap tuning. Moreover, a formation of Br-rich region on the tri-iodide perovskite layer is expected to enhance moisture stability without a loss of current density.

Mesoscopic perovskite solar cells with an admixture of nanocrystalline TiO₂ and Al₂O₃: role of interconnectivity of TiO₂ in charge collection.

Perovskite solar cells with high power conversion efficiency usually employ mesoporous TiO2, however the role of the TiO2 layer has not been clearly resolved. Here we prepared MAPbI3 (MA = CH3NH3) perovskite solar cells with an admixture of nanocrystalline TiO2 and Al2O3 to investigate the role of the mesoporous TiO2 layer. The Al2O3 content was varied from 0% (pure TiO2) to 100% (pure Al2O3) with nominal composition of (1 - x)TiO2 + xAl2O3 (x = 0, 0.

Si/Ti2O3/Reduced Graphene Oxide Nanocomposite Anodes for Lithium-Ion Batteries with Highly Enhanced Cyclic Stability.

Silicon (Si) has attracted tremendous attention as a high-capacity anode material for next generation Li-ion batteries (LIBs); unfortunately, it suffers from poor cyclic stability due to excessive volume expansion and reduced electrical conductivity after repeated cycles. To circumvent these issues, we propose that Si can be complexed with electrically conductive Ti2O3 to significantly enhance the reversible capacity and cyclic stability of Si-based anodes. We prepared a ternary nanocomposite of Si/Ti2O3/reduced graphene oxide (rGO) using mechanical blending and subsequent thermal reduction of the Si, TiO2 nanoparticles, and rGO nanosheets.

Highly Reproducible Perovskite Solar Cells with Average Efficiency of 18.3% and Best Efficiency of 19.7% Fabricated via Lewis Base Adduct of Lead(II) Iodide.

High efficiency perovskite solar cells were fabricated reproducibly via Lewis base adduct of lead(II) iodide. PbI2 was dissolved in N,N-dimethyformamide with equimolar N,N-dimethyl sulfoxide (DMSO) and CH3NH3I. Stretching vibration of S═O appeared at 1045 cm(-1) for bare DMSO, which was shifted to 1020 and 1015 cm(-1) upon reacting DMSO with PbI2 and PbI2 + CH3NH3I, respectively, indicative of forming the adduct of PbI2·DMSO and CH3NH3I·PbI2·DMSO due to interaction between Lewis base DMSO and/or iodide (I(-)) and Lewis acid PbI2.

Understanding the role of the dye/oxide interface via SnO2-based MK-2 dye-sensitized solar cells.

To understand the role of the dye/oxide interface, a model system using a nanocrystalline SnO2 and 3-hexyl thiophene based MK-2 dye is proposed. A thin interfacial TiO2 blocking layer (IBL) is introduced in between SnO2 and MK-2 and its effects on photocurrent-voltage, electron transport-recombination, and density of states (DOS) are systematically investigated. Compared to the bare SnO2 film, the insertion of IBL leads to a 14-fold improvement in the power conversion efficiency (PCE) despite little change in the dye adsorption amount, which is due to the 7-fold and 2-fold increase in the photocurrent density and voltage, respectively.

Hierarchical SnO₂ nanoparticle-ZnO nanorod photoanode for improving transport and life time of photoinjected electrons in dye-sensitized solar cell.

A hierarchical photoanode comprising a SnO(2) nanoparticle underlayer and a ZnO nanorod overlayer was prepared and its photovoltaic performance was compared to photoanodes consisting of SnO(2) nanoparticle only and ZnO nanorod only. The photoanode layer thickness was adjusted to about 7.6 μm to eliminate thickness effect.

Quantum-dot-sensitized solar cell with unprecedentedly high photocurrent.

The reported photocurrent density (J(SC)) of PbS quantum dot (QD)-sensitized solar cell was less than 19 mA/cm(2) despite the capability to generate 38 mA/cm(2), which results from inefficient electron injection and fast charge recombination. Here, we report on a PbS:Hg QD-sensitized solar cell with an unprecedentedly high J(SC) of 30 mA/cm(2). By Hg(2+) doping into PbS, J(SC) is almost doubled with improved stability.

Perceptions and behaviors related to hand hygiene for the prevention of H1N1 influenza transmission among Korean university students during the peak pandemic period.

Background: This study was performed to better assess the perceptions, motivating factors, and behaviors associated with the use of hand washing to prevent H1N1 influenza transmission during the peak pandemic period in Korea.

Methods: A cross-sectional survey questionnaire was completed by 942 students at a university campus in Suwon, Korea, between December 1 and 8, 2009. The survey included questions regarding individual perceptions, motivating factors, and behaviors associated with hand washing for the prevention of H1N1 influenza transmission.