Indium‐Free Perovskite Solar Cells Enabled by Impermeable Tin‐Oxide Electron Extraction Layers

Corrosive precursors used for the preparation of organic–inorganic hybrid perovskite photoactive layers prevent the application of ultrathin metal layers as semitransparent bottom electrodes in perovskite solar cells (PVSCs). This study introduces tin‐oxide (SnO_x) grown by atomic layer deposition (ALD), whose outstanding permeation barrier properties enable the design of an indium‐tin‐oxide (ITO)‐free semitransparent bottom electrode (SnO_x/Ag or Cu/SnO_x), in which the metal is efficiently protected against corrosion. Simultaneously, SnO_x functions as an electron extraction layer. We unravel the spontaneous formation of a PbI₂ interfacial layer between SnO_x and the CH₃NH₃PbI₃ perovskite. An interface dipole between SnO_x and this PbI₂ layer is found, which depends on the oxidant (water, ozone, or oxygen plasma) used for the ALD growth of SnO_x. An electron extraction barrier between perovskite and PbI₂ is identified, which is the lowest in devices based on SnO_x grown with ozone. The resulting PVSCs are hysteresis‐free with a stable power conversion efficiency (PCE) of 15.3% and a remarkably high open circuit voltage of 1.17 V. The ITO‐free analogues still achieve a high PCE of 11%.     

Evaluation of physicochemical,thermomechanical, and structural properties of chickpea flour composite films reinforced with crystalline nanocellulose

Chickpea flour–crystalline nano-cellulose (CNC) composite films were prepared using chickpea flour as the film forming material, glycerol as the plasticizer and 2.5 to 10% CNC as reinforcement supplement. Mechanical properties of the composite films increased with an increase in the CNC content up to 5%. By inclusion of CNC up to 10%, the storage modulus of chickpea flour matrix increased by an order of magnitude from 7.3 to 86.4 MPa. The storage modulus of all samples, on the other hand, decreased as temperature increased. The T_g values measured by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were shifted toward higher temperatures by the addition of CNC. The creep resistance of chickpea flour films increased again up to 5% added CNC, and strain sweep tests confirmed the extension of linear viscoelastic region. X- ray diffraction (XRD) confirmed a positive correlation between the degree of crystallinity of chickpea flour composties and CNC content. FTIR spectroscopy confirmed the molecular interaction between chickpea flour, glycerol and CNC. SEM results revealed agglomeration in the structure of the film with the addition of CNC beyond 5% and diminishing of surface homogeneity, while decreasing the pore size of chickpea flour matrix. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48389.     

Studies on damage and FRP strengthening of reinforced concrete beams by vibration monitoring

In this paper, modal characteristics of reinforced concrete beam specimens are identified using experimental test data. Nine concrete beam specimens were gradually damaged and the changes of dynamic parameters were monitored from initial to the failure state. Six of the specimens were strengthened with externally bonded CFRP sheets when the load reached approximately half of the predicted failure load. The identification methods based on measured modal parameters were utilized and the efficiencies of these methods were investigated. These methods include frequency changes, Modal Assurance Criterion (MAC), Coordinate Modal Assurance Criterion (COMAC) and modal curvatures. The comparison of the methods shows that the frequency changes are not fully capable of detecting damage and predicting the potency of strengthening. The MAC values can reveal the changes of overall stiffness of the beams during the load steps. The change of stiffness at each degree of freedom of beams evaluated by COMAC and modal curvatures show that the damage identification of the beam specimens is best described by modal curvature method.     

An Online Cost-Based Job Scheduling Method by Cellular Automata in Cloud Computing Environment

Wireless Personal Communications - Cloud computing has expanded considerably in industry and research and is based on a pay-as-you-go payment model. In cloud computing environment, on one hand,...     

Financial markets sentiment analysis: developing a specialized Lexicon

Journal of Intelligent Information Systems - Natural language processing in specific domains such as financial markets requires the knowledge of domain ontology. Therefore, developing a...     

Influence of position and composition on adhesion to injection-molded TPO plaques as model automotive parts

Single lap shear adhesion measurements on model isotactic polypropylene and thermoplastic polyolefin (TPO) substrates which sandwich a chlorinated polyolefin (CPO) show similar values of the fracture strength, as determined from the stress at break, but much larger deformation at break for the substrates that contain a copolymer of ethylene with 9 wt% butane (EBR9) as an impact modifier. We also found for sections cut from a large format (300 × 100 mm) plaque of TPO12 (12 wt% EBR9), that the fracture energy increased as a function of distance from the gate. ATR-FTIR measurements on these sections indicated that there was a variation in the EBR content in the near-surface region of the substrate, and that stronger adhesion correlated with an increase of EBR content at or near the surface.     

Novel 3D electrospun polyamide scaffolds prepared by 3D printed collectors and their interaction with chondrocytes

Electrospinning is significantly one of the simple and versatile methods for producing micro- and nanofibrous scaffolds. Its assembly can be modified in different ways to combine material properties with different morphological structures for biomedical applications. In this process, collector design plays an important role to determine the nanofiber orientation in electrospun nanoweb. In this work, 3D patterned scaffolds were produced by electrospinning of polyamide-66 solution on different 3D collectors that have been obtained. The aim of this work is to investigate the attachment of the chondrocyte cells on the prepared electrospun scaffolds that have different types of nanofiber orientations that could be used in tissue engineering applications.     

Sunlight photodecolorization of a mixture of Methyl Orange and Bromocresol Green by CuS incorporated in a clinoptilolite zeolite as a heterogeneous catalyst

Photocatalytic activity of CuS incorporated into an Iranian clinoptilolite (CuS-Cp) was studied for decolorization of a mixture of Methyl Orange and Bromocresol Green under sunlight irradiation. All samples were characterized by XRD, FTIR, DRS and TG/DTG techniques. The effect of some key experimental parameters such as: amount of the catalyst (0.05–5 g L^?1), initial concentration of dyes (5–30 mg L^?1), solution pH (1–11) and also dosage of H₂O₂ and KBrO₃ was studied on the decolorization extent. The extent of decolorization was estimated from the residual concentration by spectrophotometrically and it was confirmed by the reduction of chemical oxygen demand (COD).     

PLGA‐based in situ‐forming system: degradation behavior in the presence of hydroxyapatite nanoparticles

The degradation behavior of poly(lactic‐co‐glycolic acid) (PLGA) is important for its application as a biomaterial. In this work, the influence of nano‐hydroxyapatite (nano‐HA) on the degradation behavior of PLGA matrix was studied. PLGA‐based in situ forming system containing nano‐HA was prepared using the immersion precipitation method and the polymer hydrolysis was investigated in a phosphate buffer (pH 7.4) at 37°C. The pH values in the testing medium were evaluated to quantify the degradation process. Gel permeation chromatography and scanning electron microscopy techniques were employed to monitor changing of the weight‐average molecular weight (M_W) and the body structures of PLGA matrices, respectively. To model the M_W changes, a first‐order degradation model was employed. The formed PLGA matrices had different porosities that effected water penetration into the matrices following the hydrolysis process. The obtained degradation rate constant using a mathematical model for PLGA matrices with different nano‐HA content was about from 2.5 to 4.5 times lower than neat PLGA matrix. POLYM. ENG. SCI., 59:1028–1035, 2019. © 2019 Society of Plastics Engineers