Uracil Induced Simultaneously Strengthening Grain Boundaries and Interfaces Enables High-Performance Perovskite Solar Cells with Superior Operational Stability.

The operational stability is a huge obstacle to further commercialization of perovskite solar cells. To address this critical issue, in this work, uracil is introduced as a "binder" into the perovskite film to simultaneously improve the power conversion efficiency (PCE) and operational stability. Uracil can efficiently passivate defects and strengthen grain boundaries to enhance the stability of perovskite films. Moreover, the uracil also strengthens the interface between the perovskite and the Tin oxide (SnO2 ) electron transport layer to increase the binding force. The uracil-modified devices deliver a champion PCE of 24.23% (certificated 23.19%) with negligible hysteresis at active area of 0.0625 cm2 . In particular, the optimal device exhibits over 90% of its initial PCE after tracking for ≈6000 h at its maximum power point under continuous light, indicating its superior operational stability. Moreover, the devices also show great reproducibility in both PCE and operational stability.

Fully Methylammonium-Free Stable Formamidinium Lead Iodide Perovskite Solar Cells Processed under Humid Air Conditions.

Fabricating perovskite solar cells (PSCs) in ambient air condition is beneficial for lowering the processing cost and boosting the commercialization. Formamidinium lead iodide (FAPbI3) is an attractive candidate for efficient PSCs; however, it easily suffers from degradation and phase transition in the presence of ambient moisture. Methylammonium (MA) cation is commonly incorporated to stabilize FAPbI3, whereas the residual MA tends to deteriorate the thermal and operational stability. Herein, we report a MA-free strategy to fabricate high-quality α-FAPbI3 films and inverted PSCs under open air conditions with a relative humidity (RH) of 60 ± 10%. The incorporation of phenylethylammonium iodide (PEAI) effectively inhibits the decomposition and phase transition of FAPbI3 during its crystallization in humid air. Accordingly, phase-pure α-FAPbI3 perovskite films with significantly reduced δ-FAPbI3 and PbI2 content are successfully obtained. In addition, introducing PEAI strongly enhances the crystallinity of FAPbI3 perovskite films, thereby yielding enlarged grain sizes and reduced grain boundaries. Defects at the grain boundaries and surface are further passivated by PEAI addition, so that the trap state density is significantly decreased. As a result, the non-radiative recombination is effectively suppressed and the charge carrier transport is promoted. The inverted device optimized with a suitable PEAI concentration exhibits an enhanced power conversion efficiency (PCE) of 17.83%, which significantly surpasses the control device (12.29% PCE). Moreover, the PEAI optimized FAPbI3 PSCs demonstrate strongly improved long-term stability, with nearly 97% PCE maintained after 27-day storage under ambient conditions. This work provides a feasible way to fabricate PSCs in ambient air for promoting their wide range of applications.

Why is the air humid during wintertime heavy haze days in Beijing?

Atmospheric humidity has been shown to promote haze formation, but it remains unclear why the air is humid during heavy haze days in winter. Here we combine water vapor isotope measurements with WRF-Chem simulations to elucidate increasing humidity with aggravation of haze during wintertime in urban Beijing. The vapor isotopic analysis in Beijing shows that the combustion-derived water (CDW) constitutes 11.0± 6.2 % of the atmospheric moisture and its fraction in total moisture increases with aggravation of haze. Modeling results reveal that, in addition to the water vapor transported from south or east to Beijing with occurrence of haze, CDW has a considerable impact on the increasing humidity when haze becomes heavy or severe. Aerosol-radiation interactions generally decrease the water vapor content and only increase humidity with occurrence of severe haze with hourly PM2.5 concentrations exceeding 250µg m-3. Although CDW is insignificant in the global atmospheric vapor budget, it could play an important role in modifying the local weather during haze days.

A Universal Strategy of Intermolecular Exchange to Stabilize α-FAPbI3 and Manage Crystal Orientation for High-Performance Humid-Air-Processed Perovskite Solar Cells.

Preparation of high-performance perovskite solar cells without strict environmental control is an inevitable trend of commercialization. Humidity is considered the main factor hindering perovskite performance. Formamidine (FA)-based perovskites suffer from the instability of photoactive black α-FAPbI3, especially in humid air, and numerous defects in the surface and bulk of perovskite films limit their performance. In this work, long-chain n-heptylamine (nHA) is introduced via antisolvent engineering into an FA-based perovskite film. nHA removes the negative intermediate adduct and promotes the formation of α-FAPbI3 at room temperature in humid air via intermolecular exchange behavior. Moreover, the existence of nHA in the final perovskite film also reduces the defects and suppresses ion migration. The champion device delivers a power conversion efficiency (PCE) of 23.7% (certificated 22.76%) with negligible hysteresis, and the fabricated devices exhibit superior reproductivity. The device stability is also enhanced, maintaining 95% of its initial PCE after 1500 h in ambient air. Moreover, the PCE has no attenuation at the maximum power point under continuous 1-sun light soaking for 500 h. The universality of this method is also demonstrated by other perovskite compositions, including methylamine lead iodine (MAPbI3 ) and FAx MA1- x PbI3 in humid air.

The effect of magnetic field on the performance improvement of a conventional solar still: a numerical study.

Due to growing demand for potable water, the improvement of fresh water production systems such as conventional solar stills is a crucial issue. Conventional solar stills are one of the simplest methods of the production of fresh water from saline water; however, they are fairly low-performance devices. Since oxygen is a paramagnetic gas, the humid airflow in a conventional solar still can be controlled by an externally imposed magnetic field. Therefore, this paper presents the effect of magnetic field on the performance improvement of a conventional solar still as a novel technique. The governing equations of the problem are discretized by the finite volume method. The impacts of the applied magnetic field arising from a multilayer solenoid on the streamlines patterns, temperature and mass fraction contours, the production rate of water ([Formula: see text]), and the average heat transfer rate (Nu) are presented at five specified times (cases). The influences of important factors such as intensity (0≤NI≤100000) and location of the magnetic field (Xc=0.15, 0.49, and 0.83) on the heat and mass transfer rates are explored. It is found that the production rate of water and heat transfer rate are increasing functions of magnetic field intensity. For the applied magnetic field with NI = 105and Xc = 0.83 m, water productivity and convective heat transfer rate can be increased by about 43%, 38%, 41%, 40%, and 48% for cases 1, 2, 3, 4, and 5, respectively.

Hot, Humid Air Decontamination of Aircraft Confirmed That High Temperature and High Humidity Are Critical for Inactivation of Infectious, Enveloped Ribonucleic Acid (RNA) Virus.

Aims: To develop infectious (live/dead) enveloped virus test indicators and response surface methodology (RSM) models that evaluate survival of an enveloped ribonucleic acid (RNA) virus on contaminated aircraft materials after exposure to hot, humid air (HHA). Methods and Results: Enveloped RNA bacteriophage Phi6 (Φ6) was dried on wiring insulation, aircraft performance coating (APC), polypropylene, and nylon at ≥ 8 log10 plaque-forming units (PFU) test coupon-1. Only 2.4 log10 inactivation was measured on APC at 70°Celsius (°C), 5% relative humidity (RH) after 24 h. In contrast, HHA RSM models showed a 90% probability of a 7 log10 inactivation at ≥63°C, 90% RH after 1 h, and decontamination kinetics were similar across different materials. HHA decontamination of C-130 and C-17 aircraft showed >7 log10 and ≥5.9 log10 inactivation of enveloped virus on 100 and 110 test indicators, respectively, with a 1-h treatment, excluding ramp-up and ramp-down times. Conclusions: Enveloped RNA virus test indicators were successfully developed, lab tested for HHA decontamination, analyzed for RSM, and field-tested in aircraft demonstrations. Significance and Impact of the Study: The utility of HHA decontamination was demonstrated after inactivating enveloped RNA virus on aircraft with a 1-h HHA treatment within aircraft temperature and RH limits.

Synergy Effect of Au and SiO2 Modification on SnO2 Sensor Properties in VOCs Detection in Humid Air.

Nanocomposites based on Au- and SiO2-modified SnO2 were studied as sensitive materials for ethanol and benzene detection in dry (RH = 1%) and humid (RH = 20%) air. Modification of SnO2 by amorphous SiO2 (13 mol.%) was effectuated by hydrothermal synthesis; modification by Au nanoparticles (1 wt.%) was carried out via impregnation by citrate-stabilized Au sol. The composition of the samples was determined by X-ray fluorescent spectroscopy and energy-dispersive X-ray spectroscopy. The microstructure was characterized by XRD, HRTEM, and low-temperature nitrogen adsorption. The surface groups were investigated by XPS, TPR-H2, and FTIR spectroscopy. DRIFT spectroscopy was performed to investigate the interaction between ethanol and the surface of the synthesized materials. Studies of the sensor properties have shown that in all cases the most sensitive is the SnO2/SiO2-Au nanocomposite. This material retains high sensitivity even in a humid atmosphere. The obtained results are discussed in terms of the synergistic effect of two modifiers (Au and SiO2) in the formation of sensor properties of SnO2/SiO2-Au nanocomposites.

Combining spore germination and heat inactivation to decontaminate materials contaminated with Bacillus anthracis spores.

AIMS: To add a spore germination step in order to reduce decontamination temperature and time requirements compared to the current hot, humid air decontamination parameters, which are 75-80°C, ≥72 h, 70-90% RH, down to ≤60°C and ≤24 h total decontamination time. METHODS AND RESULTS: Bacillus anthracis spore germination with l-alanine+inosine+calcium dipicolinate (CaDPA) was quantified at 0-40°C, several time points and spore concentrations of 5-9 log10 per ml. Germination efficiency at 0-40°C was >99% at <8 log10 spores per ml. The temperature optimum was 20°C. Germination efficiency was significantly higher but slower at 0°C compared to ≥30°C at ≥8 log10 spores per ml. A single germinant application followed by 60°C, 1-h treatment consistently inactivated >2 log10 (>99%) of spores. However, a repeat application of germinant was needed to achieve the objective of ≥6 log10 spore inactivation out of a 7 log10 challenge (≥99·9999%) for ≤24 h total decontamination time for nylon and aircraft performance coating. CONCLUSIONS: l-alanine+inosine+CaDPA stimulated germination across wide temperature and spore concentration ranges. SIGNIFICANCE AND IMPACT OF THE STUDY: Germination expands the scope of spore decontamination to include materials from any industry sector that can be sprayed with an aqueous germinant solution.

Experimental study of humidity effect on charge measurement of reference ionization chambers in clinical high-energy photon beams.

PURPOSE: In the practice code of dosimetry, humidity effect is assumed to be constant as far as the measurements are performed in the relative humidity (RH) range of (20-80)%; thus, the humidity effect can be ignored with a dose uncertainty of 0.15%. This assumption is based on the previous experimental results by Niatel and Guiho. Rogers and Ross calculated the stopping power ratio of humid air and dry air for high-energy electron beams by using a Monte Carlo code. They demonstrate that the W value, the mean energy required to create an ion pair in air, is independent of the beam quality when the air is dry, and that the traditional humidity correction can be used also for high-energy photon and electron beams; however, this was only a computational study. In the present study, we measured the humidity correction of Farmer-type ionization chambers in high-energy photon beams and determined the W values of humid air using the calculated energy deposition of humid air with a Monte Carlo code. Furthermore, we proposed an analytical expression to determine a practical humidity correction for an ionization chamber as a function of absolute humidity. METHOD: Experiments were carried out using a clinical linear accelerator (linac, Elekta Precise) at the National Metrology Institute of Japan (NMIJ). A shield box was constructed downstream of the linac and connected to an air processor, which maintained the temperature around 22°C and controlled the humidity in the range of (10-70)% inside the box. We prepared two Farmer-type ionization chambers: PTW 30013 and Exradin A19. Each ionization chamber was placed inside the box and irradiated with 6-, 10-, and 15-MV high-energy photon beams from the clinical linac. The energy deposition to the humid air inside the ionization chamber was calculated using the Electron Gamma Shower Version 5 (EGS5) code system. RESULTS: Stabilization for the humidity of the ionization chamber was completed within 3 h. The polarity and ion recombination corrections did not show any change in the humidity range studied. The measured humidity correction and the evaluated W values of humid air in high-energy photon beams were in good agreement with those by Rogers in TG-21 and by Niatel in the range of RH (10-70)%. CONCLUSION: Humidity correction of ionization chambers in high-energy photon beams from the clinical linac was determined experimentally. Using the analytical expression for the energy depositions by EGS5, the analytical expression for the W values was also derived.

Adsorption/desorption kinetics and breakthrough of gaseous toluene for modified microporous-mesoporous UiO-66 metal organic framework.

In this work, micro-mesoporous UiO-66 was successfully prepared with P123 (EO20PO70EO20) as structure-directing agent by a simple solvothermal method. Adsorption/desorption kinetics of gaseous toluene over pristine UiO-66 and micro-mesoporous UiO-66 were investigated by breakthrough experiments, toluene vapor adsorption isotherm measurements and temperature programmed desorption (TPD) experiments. The interactions between toluene and UiO-66 samples were assessed through the Henry's law constant (KH) and the isosteric adsorption heat (ΔHads). The micro-mesoporous UiO-66 crystal demonstrated 2.6 times toluene adsorption capacity of the pristine UiO-66 when the P123/Zr4+ molar ratio was 0.2. Results showed that micropore adsorption was the main adsorption process and the larger pores in micro-mesoporous UiO-66 increased molecular diffusion rate and reduced the mass transfer resistance. This result indicated that micro-mesoporous structures and defect sites had a positive effect on toluene molecules capture. The breakthrough times and the working capacities decreased with the increase of the relative humidity and adsorption temperature. A good thermal stability and reproducibility were revealed over the micro-mesoporous UiO-66 in this paper.

Enhanced hydrophobic UiO-66 (University of Oslo 66) metal-organic framework with high capacity and selectivity for toluene capture from high humid air.

Metal organic frameworks (MOFs) are good absorbents that provide high specific surface area, modified pore surface and controllable pore size. The aim of this work is to prepare a MOFs material with good toluene adsorption property in the presence of water. In this paper, modified UiO-66 (University of Oslo 66) was successfully synthesized with polyvinylpyrrolidone (PVP) as structure-directing agent by a simple solvothermal method. The physical and chemical properties were obtained by a series of characterization instruments. Some missing-linker defect sites were observed on modified materials (defective UiO-66) and were known as the main active sites for toluene adsorption. The defective UiO-66 (PVP-U-0.5, 259 mg g-1) demonstrated 1.7 times toluene adsorption capacity of the pristine UiO-66 (151 mg g-1) when the PVP/Zr4+ ratio was 0.5. The interactions between toluene and UiO-66 and PVP-U-0.5 were assessed through the Henry's law constant (KH) and the isosteric adsorption heat (ΔHads), which indicated that stronger interaction between PVP-U-0.5 and toluene molecules. Moreover, PVP-U-0.5 displayed good adsorption capacity (84 mg g-1) at high relative humidity (70% RH). Water temperature programmed desorption experiments revealed that PVP-U-0.5 had more hydrophobic property, which provided a further possibility for practical application for the removal of toluene.

Poly(3-Methylthiophene) Thin Films Deposited Electrochemically on QCMs for the Sensing of Volatile Organic Compounds.

Poly(3-methylthiophene) (PMeT) thin films were electrochemically deposited on quartz crystal microbalance QCM transducers to investigate their volatile organic compound (VOC) sensing properties depending on ambient conditions. Twelve different VOCs including alcohols, ketones, chlorinated compounds, amines, and the organosphosphate dimethyl methylphosphonate (DMMP) were used as analytes. The responses of the chemical sensors against DMMP were the highest among the tested analytes; thus, fabricated chemical sensors based on PMeT can be evaluated as potential candidates for selectively detecting DMMP. Generally, detection limits in the low ppm range could be achieved. The gas sensing measurements were recorded at various humid air conditions to investigate the effects of the humidity on the gas sensing properties. The sensing performance of the chemical sensors was slightly reduced in the presence of humidity in ambient conditions. While a decrease in sensitivity was observed for humidity levels up to 50% r.h., the sensitivity was nearly unaffected for higher humidity levels and a reliable detection of the VOCs and DMMP was possible with detection limits in the low ppm range.

Hot, humid air decontamination of a C-130 aircraft contaminated with spores of two acrystalliferous Bacillus thuringiensis strains, surrogates for Bacillus anthracis.

AIM: To develop test methods and evaluate survival of Bacillus thuringiensis kurstaki cry(-) HD-1 and B. thuringiensis Al Hakam spores after exposure to hot, humid air inside of a C-130 aircraft. METHODS AND RESULTS: Bacillus thuringiensis spores were either pre-inoculated on 1 × 2 or 2 × 2 cm substrates or aerosolized inside the cargo hold of a C-130 and allowed to dry. Dirty, complex surfaces (10 × 10 cm) swabbed after spore dispersal showed a deposition of 8-10 log10 m(-2) through the entire cargo hold. After hot, humid air decontamination at 75-80°C, 70-90% relative humidity for 7 days, 87 of 98 test swabs covering 0·98 m(2) , showed complete spore inactivation. There was a total of 1·67 log10 live CFU detected in 11 of the test swabs. Spore inactivation in the 98 test swabs was measured at 7·06 log10 m(-2) . CONCLUSIONS: Laboratory test methods for hot, humid air decontamination were scaled for a large-scale aircraft field test. The C-130 field test demonstrated that hot, humid air can be successfully used to decontaminate an aircraft. SIGNIFICANCE AND IMPACT OF THE STUDY: Transition of a new technology from research and development to acquisition at a Technology Readiness Level 7 is unprecedented.

Test methods and response surface models for hot, humid air decontamination of materials contaminated with dirty spores of Bacillus anthracis ∆Sterne and Bacillus thuringiensis Al Hakam.

AIMS: To develop test methods and evaluate survival of Bacillus anthracis ∆Sterne or Bacillus thuringiensis Al Hakam on materials contaminated with dirty spore preparations after exposure to hot, humid air using response surface modelling. METHODS AND RESULTS: Spores (>7 log10 ) were mixed with humic acid + spent sporulation medium (organic debris) or kaolin (dirt debris). Spore samples were then dried on five different test materials (wiring insulation, aircraft performance coating, anti-skid, polypropylene, and nylon). Inoculated materials were tested with 19 test combinations of temperature (55, 65, 75°C), relative humidity (70, 80, 90%) and time (1, 2, 3 days). The slowest spore inactivation kinetics was on nylon webbing and/or after addition of organic debris. CONCLUSIONS: Hot, humid air effectively decontaminates materials contaminated with dirty Bacillus spore preparations; debris and material interactions create complex decontamination kinetic patterns; and B. thuringiensis Al Hakam is a realistic surrogate for B. anthracis. SIGNIFICANCE AND IMPACT OF THE STUDY: Response surface models of hot, humid air decontamination were developed which may be used to select decontamination parameters for contamination scenarios including aircraft.

Response surface modeling for hot, humid air decontamination of materials contaminated with Bacillus anthracis ∆Sterne and Bacillus thuringiensis Al Hakam spores.

Response surface methodology using a face-centered cube design was used to describe and predict spore inactivation of Bacillus anthracis ∆Sterne and Bacillus thuringiensis Al Hakam spores after exposure of six spore-contaminated materials to hot, humid air. For each strain/material pair, an attempt was made to fit a first or second order model. All three independent predictor variables (temperature, relative humidity, and time) were significant in the models except that time was not significant for B. thuringiensis Al Hakam on nylon. Modeling was unsuccessful for wiring insulation and wet spores because there was complete spore inactivation in the majority of the experimental space. In cases where a predictive equation could be fit, response surface plots with time set to four days were generated. The survival of highly purified Bacillus spores can be predicted for most materials tested when given the settings for temperature, relative humidity, and time. These predictions were cross-checked with spore inactivation measurements.

Initial oxidation of brass induced by humidified air.

Complementary surface and near-surface analytical techniques have been used to explore a brass (Cu-20Zn) surface before, during, and after exposure in air at 90% relative humidity. Volta potential variations along the unexposed surface are attributed to variations in surface composition and resulted in an accelerated localized growth of ZnO and a retarded more uniform growth of an amorphous Cu2O-like oxide. After 3 days the duplex oxide has a total mass of 1.3 µg/cm2, with improved corrosion protective properties compared to the oxides grown on pure Cu or Zn. A schematic model for the duplex oxide growth on brass is presented.

High accuracy acoustic relative humidity measurement in duct flow with air.

An acoustic relative humidity sensor for air-steam mixtures in duct flow is designed and tested. Theory, construction, calibration, considerations on dynamic response and results are presented. The measurement device is capable of measuring line averaged values of gas velocity, temperature and relative humidity (RH) instantaneously, by applying two ultrasonic transducers and an array of four temperature sensors. Measurement ranges are: gas velocity of 0-12 m/s with an error of ± 0.13 m/s, temperature 0-100 °C with an error of ± 0.07 °C and relative humidity 0-100% with accuracy better than 2 % RH above 50 °C. Main advantage over conventional humidity sensors is the high sensitivity at high RH at temperatures exceeding 50 °C, with accuracy increasing with increasing temperature. The sensors are non-intrusive and resist highly humid environments.