Improvement of stability for organic solar cells by using molybdenum trioxide buffer layer

We demonstrated that the stability of organic solar cells (OSCs) under light irradiation is markedly enhanced by inserting a molybdenum trioxide (MoO₃) buffer layer between an anode layer of indium tin oxide (ITO) and a p-type layer of 5,10,15,20-tetraphenylporphyrin (H₂TPP) or N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD). The use of the MoO₃ layer also enhanced open-circuit voltages and power conversion efficiencies of the OSCs due to an increase in built-in potential. From results of stability test of hole-only α-NPD devices, we concluded that the OSC degradation occurs near the ITO/p-type layer interface and that the use of the MoO₃ layer can prevent the degradation at this interface.     

The viscoelastic properties of soybean curd (tofu) as affected by soymilk concentration and type of coagulant

The viscoelastic properties of different types of tofu were investigated. Soymilk concentrations were 5, 6, 7, 8 and 9%. Coagulants used were 30 mm CaSO₄ or 30 mm glucono‐delta‐lactone (GDL). As the concentration of soymilk was increased viscosity and handling difficulties increased. A high concentration of soymilk in tofu gave a high break stress and produced hard tofu. The four‐element Burgers model fitted the creep behaviour and both viscous and elastic parameters could be acquired from model analysis, reflecting changes in elasticity and viscosity of tofu. The constant viscous parameter in the model increased with increasing soymilk concentration. The viscous parameters of viscoelastic materials like tofu gel, obtained from small deformation tests, seemed to correlate, to some extent, with the break stress obtained from large deformation tests. For hard tofu production increasing the soymilk concentration within a certain range and the partial replacement of calcium sulphate coagulant by GDL could be effective options.     

Evaluation of experimentally obtained permeance based on module simulation: How should permeance be evaluated?

Permeance and permeance ratio in binary separation generally are obtained from experimental data using an analytical permeance equation consisting of the logarithmic average of the partial pressure difference (hereafter, approximate permeance equation). The aim of the present study was to clarify the applicable range for this equation. First, the separation performance of a membrane module was calculated with various given membrane properties (permeance, permeance ratio) and operation conditions (pressure, flow rate) via numerical computation. The obtained concentrations and flow rates in the retentate and permeate were used to calculate permeances via approximate permeance equation, and the validity was discussed by comparing permeances used for numerical computation with obtained ones. The present work clarifies the validity of the approximate permeance equation, and yields a general guideline stipulating that the partial pressure difference across the membrane at the inlet and outlet should maintain more than 60% to obtain the correct permeance.     

Evaluating the chemical stability of metal oxides in SO3 and applications of SiO2-based membranes to O2/SO3 separation

The decomposition of sulfur trioxide to produce sulfur dioxide and oxygen using a catalytic membrane reactor is technology that promises to improve the economic viability of the thermochemical water-splitting Iodine-Sulfur (IS) process for large-scale CO₂-free hydrogen production. The chemical stability of membrane materials under SO₃, however, is a significant challenge for this strategy. In this study, microporous membranes with a layered structure that consisted of a membrane support prepared from α-Al₂O₃, an intermediate layer prepared from silica-zirconia, and a top layer prepared from bis (triethoxysilyl)ethane-derived organosilica sols, were examined for stability under SO₃ and for use in SO₃/O₂ separation. An α-Al₂O₃ support that features SiO₂–ZrO₂ intermediate layers with large pore sizes and a high Si/Zr molar ratio showed excellent resistance to SO₃, which was confirmed by N₂ adsorption, Energy Dispersive X-ray Spectroscopy (EDS), and Scanning Electron Microscopy (SEM). These membranes also demonstrated a negligible change in gas permeance before and after SO₃ exposure. Subsequently, in binary-component gas separation at 550°C, microporous organosilica-derived membranes achieved an O₂/SO₃ selectivity of 10 (much higher than the Knudsen selectivity of 1.6) while maintaining a high O₂ permeance of 2.5 × 10⁻⁸ mol m^–2 s^–1 Pa^–1.     

Comparison of color-appearance models

The color-appearance models developed by R. W. G. Hunt (model H) and Y. Nayatoni and his collaborators (model N) are compared. The following color perceptions are analyzed: (1) colorfulness under illuminant C for NCS samples, (2) colorfulness change by changing illuminant C to illuminant A, (3) colorfulness change by changing adaptign illuminance, (4) Helson-Judd effect on achromatic colors under saturated chromatic illuminants, and (5) brightness and lightness. Special features of each model are made clear. In addition, a deatailed discussion is given on the mechanism introbucing the Helson-Judd effect and on the model formulations, especially in model H.     

Simultaneous Edge‐on to Face‐on Reorientation and 1D Alignment of Small π‐Conjugated Molecules Using Room‐Temperature Mechanical Rubbing

In this study, room‐temperature mechanical rubbing is used to control the 3D orientation of small π‐conjugated molecular systems in solution‐processed polycrystalline thin films without using any alignment substrate. High absorption dichroic ratio and significant anisotropy in charge carrier mobilities (up to 130) measured in transistor configuration are obtained in rubbed organic films based on the ambipolar quinoidal quaterthiophene (QQT(CN)4). Moreover, a solvent vapor annealing treatment of the rubbed film is found to improve the optical and charge transport anisotropy due to an increased crystallinity. X‐ray diffraction and atomic force microscopy measurements demonstrate that rubbing does not only lead to an excellent 1D orientation of the QQT(CN)4 molecules over large areas but also modifies the orientation of the crystals, moving molecules from an edge‐on to a face‐on configuration. The reasons why a mechanical alignment technique can be used at room temperature for such a polycrystalline film are rationalized, by the plastic characteristics of the QQT(CN)4 layer and the role of the flexible alkyl side chains in the molecular packing. This nearly complete conversion from edge‐on to face‐on orientation by mechanical treatment in polycrystalline small‐molecule‐based thin films opens perspectives in terms of fundamental research and practical applications in organic optoelectronics.     

Enhanced Electroluminescence from Organic Light‐Emitting Diodes with an Organic–Inorganic Perovskite Host Layer

The development of host materials with high performance is essential for fabrication of efficient and stable organic light‐emitting diodes (OLEDs). Although host materials used in OLEDs are typically organics, in this study, it is shown that the organic–inorganic perovskite CH₃NH₃PbCl₃ (MAPbCl₃) can be used as a host layer for OLEDs. Vacuum‐evaporated MAPbCl₃ films have a wide band gap of about 3 eV and very high and relatively balanced hole and electron mobilities, which are suitable for the host material. Photoluminescence and electroluminescence take place through energy transfer from MAPbCl₃ to an organic emitter in films. Incorporation of an MAPbCl₃ host layer into OLEDs leads to a reduction of driving voltage and enhancement of external quantum efficiency as compared to devices with a conventional organic host layer. Additionally, OLEDs with an MAPbCl₃ host layer demonstrate very good operational stability under continuous current operation. These results can be extensively applied to organic‐ and perovskite‐based optoelectronics.     

间冷冰箱回风道的优化除霜设计

间冷冰箱蒸发器霜层分布对除霜加热器除霜热量分布的不一致性会导致除霜时间增加和除霜效率的降低,因此,本文提出一种间冷式冰箱回风道的优化除霜设计方法。首先通过实验测量除霜加热器表面温度分布,确定除霜加热器除霜热量分布,进而确定与除霜热量相匹配的蒸发器结霜分布;然后基于蒸发器结霜分布确定回风道出口的最优风量分布;最后基于最优的风量分布设计回风道,使蒸发器上霜层分布与除霜加热器除霜热量分布相一致,达到优化除霜的目的。通过某间冷冰箱回风道的优化设计案例表明,优化后的回风道可实现出口风量分布与除霜加热器除霜热量分布相匹配,除霜时间缩短了38.9%,同时使冰箱的制冷量增加了3.43%。     

Deployment of wireless mesh network using RSSI-based swarm robots

This paper proposes a novel method for deploying a wireless mesh network (WMN) using a group of swarm robots equipped with wireless transceivers. The proposed method uses the rough relative positions of the robots estimated by their Radio Signal Strength Indicators (RSSIs) to deploy the WMN. The employed algorithm consists of three parts, namely, (1) a fully distributed and dynamic role decision method among the robots, (2) an adaptive direction control using the time difference of the RSSIs, and (3) a narrow corridor for the robots to pass by movement function along walls. In our study, we evaluated the performances of the proposed deployment method and a conventional method in a real environment using 12 real robots for simple deployment, and 10 real robots for passing the narrow corridor. The results of the performed experiments showed that (1) the proposed method outperformed the conventional method with regard to the deployment time, power consumption, and the distances traveled by the robots, and (2) the movement function along the walls is effective while passing a narrow corridor unlike any other function.     

Gas permeation properties for organosilica membranes with different Si/C ratios and evaluation of microporous structures

Organosilica membranes were fabricated using bridged organoalkoxysilanes (bis(triethoxysilyl)methane (BTESM), bis(triethoxysilyl)ethane (BTESE), bis(triethoxysilyl)propane (BTESP), bis(trimethoxysilyl)hexane (BTMSH), bis(triethoxysilyl)benzene (BTESB), and bis(triethoxysilyl)octane (BTESO)) to produce highly permeable molecular sieving membranes. The effect of the organoalkoxysilanes on network pore size and microporous structure was evaluated by examining the molecular size and temperature dependence of gas permeance across a wide range of temperatures. Organosilica membranes showed H₂/N₂ and H₂/CH₄ permeance ratios that ranged from 10 to 150, corresponding to network pore size, and both H₂ selectivity decreased with an increase in the carbon number between 2 Si atoms. Organosilica membranes showed activated diffusion for He and H₂, and a slope of temperature dependence that increased approximate to the increase in the carbon number between 2 Si atoms. The relationship between activation energy and He/H₂ permeance ratio for SiO₂ and organosilica membranes suggested that the molecular sieving can dominate He and H₂ permeation properties via the rigid microporous structure, which was constructed by BTESM and BTESE. With increased in the carbon concentration in silica, polymer chain vibration in organic bridges, which is a kind of solution/diffusion mechanism, can dominate the permeation properties. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4491–4498, 2017