Compact Film Research Articles

Sb2 Se3 Thin-Film Solar Cells Exceeding 10% Power Conversion Efficiency Enabled by Injection Vapor Deposition Technology.

Binary Sb2 Se3 semiconductors are promising as the absorber materials in inorganic chalcogenide compound photovoltaics due to their attractive anisotropic optoelectronic properties. However, Sb2 Se3 solar cells suffer from complex and unconventional intrinsic defects due to the low symmetry of the quasi-1D crystal structure resulting in a considerable voltage deficit, which limits the ultimate power conversion efficiency (PCE). In this work, the creation of compact Sb2 Se3 films with strong [00l] orientation, high crystallinity, minimal deep level defect density, fewer trap states, and low non-radiative recombination loss by injection vapor deposition is reported. This deposition technique enables superior films compared with close-spaced sublimation and coevaporation technologies. The resulting Sb2 Se3 thin-film solar cells yield a PCE of 10.12%, owing to the suppressed carrier recombination and excellent carrier transport and extraction. This method thus opens a new and effective avenue for the fabrication of high-quality Sb2 Se3 and other high-quality chalcogenide semiconductors.

Experimental and theoretical investigations on fullerene (C60) induced compact CH3NH3PbI3 perovskite thin films

In the present work, pure and Fullerene (C60)-doped methyl ammonium lead halide (CH3NH3PbI3) perovskite thin films were prepared on glass substrates by spin coating method at different concentrations of fullerene (C60).The structural, morphological, and optical characteristics of as-prepared thin films were analysed using experimental and computational methods. The X-ray diffraction studies and their Reitveld refinement analysis of the samples confirms that all deposited perovskite thin films have tetragonal structure and are highly oriented along the (110) plane. The morphology of the perovskite films was investigated by field emission scanning electron microscope (FE-SEM). The elemental composition of perovskite thin films was confirmed by Energy Dispersive X-rays Analysis (EDAX). The addition of fullerene (C60) resulted in the increase of grain size sand a more compact surface development of the perovskite thin films with fewer flaws as compared with perovskite thin films without (C60) was evaluated. Also, geometrical, electronic and optical properties were studied by using the first principles DFT computational method. Optical properties have been studied experimentally and verified computationally. All the perovskite thin film samples exhibit direct band-gap which is suitable for solar cells applications.

The impact of laser-scribing carbon-based supercapacitor electrodes

In highly porous carbon electrodes, a large fraction of pores can be inaccessible to the electrolyte, which translates into lower specific capacitances. This is accentuated at high current densities. To circumvent this, channels can be opened to enhance ionic diffusion. In this work, ionic channels were created using a pulsed laser. Nine sets of laser-scribing parameters (pulse fluence and spot spacing) were applied on two sets of carbon-based supercapacitor electrodes: K-bar hand-coated electrodes (“K”) and screen-printed electrodes (“SP”). Profilometry and scanning electron microscopy revealed that, before laser-scribing, the latter already had several holes and trenches, whilst the former were compact films. Electrochemical measurements in Na2SO4 indicate improvements in the rate capability of the laser-scribed SP electrodes, namely an up to 50% reduction of the rate at which energy density decreases as power densities increase. For laser-scribed K electrodes, the slope of the Ragone plot only decreased by ca. 20% in the best set of conditions. However, for both sets of electrodes, a negative trade-off is observed: laser processed electrodes seem to have a lower specific capacitance. This might be caused by the entrapment of debris in the laser-drilled holes, which could lead to the overestimation of the active mass. Moreover, X-ray Photoelectron Spectroscopy analysis suggests that this may also be explained by the decrease in the oxygen functionalities and by its impact on the electrodes’ wettability. On the other hand, for electrodes tested in an organic electrolyte (tetrabutylammonium perchlorate in acetonitrile), the specific capacitance at 2 A/g was up to 66% higher for laser-scribed electrodes and an energy density of 13 Wh/kg was achieved even at 2.8 kW/kg.

Chitosan biomolecules-modified graphene oxide nano-layers decorated by mesoporous ZIF-9 nanocrystals for the construction of a smart/pH-triggered anti-corrosion coating system

The present research has focused on introducing a novel carbon nano-filler modified by stable nano-crystals based on Co-based MOF (called ZIF-9). For improving the GO dispersion, the graphene layers were modified with chitosan (CS-rGO) and then decorated with MOF particles. The fabricated hybrid particles' structures were probed by detailed spectroscopic techniques (i.e., XRD, UV–Vis, Raman, and FT-IR) and the morphology was observed by FE-SEM. The zeta potential and UV–Vis/ICP achievements displayed the pH sensitivity of the constructed ZIF-9@CS-rGOs structure. The solution phase electrochemical explorations displayed the ZIF-9@CS-rGO nanoparticles' effectiveness in anodic reaction rate mitigation, providing corrosion resistance around 4100 Ω.cm2 in the best condition (EIS), and the FE-SEM images have proved that a high compact film generation could result in the steel surface damage control in chloride media. The active protection ability of the ZIF-9@CS-rGO/EP scratched composite was explored by EIS approaches and the scratched line morphology was probed by aiding FE-SEM. Outcomes have displayed that the scratched composite resistance was raised to 89000 Ω.cm2 after ZIF-9@CS-rGO inclusion and FE-SEM micrographs have displayed sufficient scratched line surface coverage. Also, the intact ZIF-9@CS-rGO/EP composite coating resistance was improved to 26 MΩ.cm2, confirming the notable EP pathways blockage after introducing ZIF-9@Cs-rGO nano-filler.

Anti-Corrosive Effects of Calcareous Deposit Films Formed by Electrodeposition in Submerged and Tidal Zones

In this study, homogeneous calcareous deposit films were formed via electrodeposition, and the characteristics of the films were studied using various surface analytical techniques. In addition, the optimal conditions were determined, and the anti-corrosive effect was confirmed via electrodeposition to form uniform and compact aragonite films in marine environments such as submerged and tidal zones. The calcareous deposit films formed in the tidal zone were thinner compared to those formed in the submerged zone. However, the aragonite–CaCO3 ratio in the tidal zone was high and the films were firm and dense. The adhesion properties were excellent at 3 and 1 A/m2, and the current density was reduced by more than 90% because the films were formed on the steel surface.

Low Threshold and Ultrastability of One-Step Air-Processed All-Inorganic CsPbX3 Thin Films toward Full-Color Visible Amplified Spontaneous Emission

All-inorganic perovskites (CsPbX3) with the merits of high stability and remarkable optical gain property are attractive for achieving on-chip coherent light sources. Unfortunately, traditional solution-processed CsPbX3 films suffer from inevitable poor surface integrity and pinhole defects, severely hindering their optical properties. Here, from the perspective of precursor solution chemistry, we use an ionic liquid solvent methylammonium acetate (MAAc) to fabricate compact, pinhole-free, and smooth CsPbX3 thin films in a one-step air process without antisolvent treatment. Optically pumped amplified spontaneous emission (ASE) with a straightforward visible spectral tunability (418-725 nm) is achieved under both nanosecond and femtosecond laser excitation. For the representative CsPbBr3 films, the threshold reaches down to 11.4 μJ cm-2 under nanosecond laser pumping, which is comparable to the value under one-photon femtosecond pumping. The long gain lifetime up to 258.2 ps is revealed by transient absorption spectroscopy. Most importantly, the films show excellent optical stability and humidity stability with no obvious degradation under the pulsed laser irradiation for more than 210 min, stable ASE output under 95% high humidity, and conspicuous ASE after 1000 h of storage in air condition without encapsulation. These results demonstrate that the method of fabricating inorganic perovskite films with an ionic liquid solvent is promising in developing high-performance full-color visible lasers.

Fabrication and properties of compact (CH3NH3)3Bi2I9 perovskite solar cell by the hot immersion method

In this paper, the performance of the methylammonium bismuth iodide (MBI) solar cells device fabricated using the hot immersion method (HIM) is evaluated for the first time. The hot immersion time (HIT) varied between 1 h and 24 h to obtain a compact MBI film. The scanning electron microscopy images visually depicted that the compact MBI film was fabricated at 24 h. The cross-sectional SEM image confirmed the uniformity and smoothness of the film, while the Dektak measurement revealed that the surface roughness decreased as the HIT was increased to 24 h. The crystallinity of the MBI film showed much improvement and UV–vis showed the extended absorption of light towards the visible region. The performance of MBI solar cells indicates five times and four times increment in the voltage and the efficiency, respectively. Our findings provide a new route to design a better absorber film in the bismuth-perovskite solar cells (Bi-PeSCs) device development using a simple method in the future.

Highly Responsive Pd-Decorated MoO3 Nanowall H2 Gas Sensors Obtained from In-Situ-Controlled Thermal Oxidation of Sputtered MoS2 Films.

Among transition metal oxides, MoO3 is a promising material due to its layered structure and different oxidation states, making it suitable for different device applications. One of the methods used to grow MoO3 is radio frequency magnetron sputtering (RFMS), which is the most compatible method in industry. However, obtaining nanostructures by RFMS for metal oxides is challenging because of compact morphology film formation. In this study, α-MoO3 with vertical nanowalls is obtained by a two-step process; deposition of magnetron-sputtered MoS2 vertical nanowalls and postoxidation of these structures without changing the morphology. In situ transmittance and electrical measurements are performed to control the oxidation process, which shed light on understanding the oxidation of MoS2 nanowalls. The transition from MoS2 to α-MoO3 is investigated with partially oxidized MoS2/MoO3 samples with different thicknesses. It is also concluded that oxidation starts from nanowalls perpendicular to the substrate and lasts with oxidation of basal planes. Four different thicknesses of α-MoO3 nanowall samples are fabricated for H2 gas sensors. Also, the effect of Pd deposition on the H2-sensing properties of sensors is deeply investigated. An outstanding response of 3.3 × 105 as well as the response and recovery times of 379 and 304 s, respectively, are achieved from the thinnest Pd-loaded sample. Also, the gas-sensing mechanism is explored by gasochromic measurements to investigate the sensor behaviors under the conditions of dry air and N2 gas as the carrier gas.

Low-pressure hollow cathode plasma source carburizing of AISI 304L austenitic stainless steel at low temperature

A carburizing treatment of AISI 304L austenitic stainless steel was performed at a low temperature of 450 °C using the low-pressure hollow cathode plasma source technique. The hollow cathode plasma was produced in a cathodic cage made of stainless steel screen inlaid with a stainless steel tubes array. A pulsed high voltage power, with a peak voltage of 800 V and a pulse frequency of 30 kHz, was applied at a low gas pressure of 50 Pa. The austenitic stainless steel samples were carburized with a direct current bias of −200 V under the CH4/H2 ratio changing in a range from 0.11 to 9, for a carburizing time of 4 h. Under the lower CH4/H2 ratio of 0.11, a diamond-like carbon film of approximately 260 nm thick formed on the stainless steel surface. As the CH4/H2 ratio increased to 0.67 and 1, both carburizing cases possessed a similar thickness of about 11 μm, with the surface carbon concentration being 6 to 6.5 at.%. A layer of carbon supersaturated face-centered-cubic (γC) phase formed, together with carbon-rich (Fe,Cr)5C2 carbide precipitation. Under the highest CH4/H2 ratio of 9, a single γC phase layer was obtained in a carburizing case of similar thickness, with a high surface carbon concentration of 7.5 at.%. The maximum surface hardness value of HV0.25 N 7.1 GPa occurred on the single γC phase layer. No pitting corrosion occurred on the single γC phase in the polarization curve. The higher passive film resistance and the lower donor and acceptor concentrations and flat band potential indicated that a more compact passive film is grown on the γC phase layer. The (Fe,Cr)5C2 carbide precipitates in the γC phase matrix degraded the passivity of the γC phase layer due to the reduced compactness of the passive film. A carbon transport competition mechanism between carbon adsorption onto the surface and carbon inward diffusion that was mainly dependent on the heavier CHn+ ion bombardment, was proposed to explain the transition with increasing CH4/H2 ratio from carbon film deposition, to a carburizing case composed of ae single γC phase, with both increased hardness and higher corrosion resistance.

Effect of Nb on the surface composition of FeCrAl alloys after anodic polarization

XPS combined with AFM have been used to investigate the surface modifications of nuclear grade FeCrAl-xNb (x= 0, 0.5, 1.0, 1.5 wt.%) alloys, induced by anodic polarization in a simulated primary coolant. Electrochemical tests were performed to study the role of the minor element Nb on the corrosion potential and composition. The optimal content of Nb, obtained after the comparative analysis of the UHV-sputtered surface, native oxide-covered surface and anodic polarized surface, is 0.5 wt.%. This alloy presents a more compact Al-enriched oxide film consistent with a higher corrosion potential at −89 mV. The protectiveness of oxide film against the active dissolution can be improved by Nb addition, but does not increases linearly with Nb content. High resolution XPS analysis details the changes of Nb oxidized states, and provides the stratification of the oxide film containing the (hydr) oxides of Fe, Al and Cr.

Effect of Ce addition on the high‐temperature oxidation resistance of Mg–Gd alloys

AbstractIn the present study, the oxidation resistance of magnesium alloyed with Gd and Ce was investigated. The high‐temperature oxidation resistance of Mg–3.5Gd–xCe (x = 0, 0.2, 0.4, 0.7 and 1.0 wt%) alloys was evaluated at temperatures between 550°C and 650°C. Results indicate that adding less than 0.7 wt% Ce resulted in high oxidation resistance, whereas the Ce addition exceeding 0.7 wt% deteriorated the oxidation resistance. The high oxidation resistance phenomenon is attributed to the formation of compact oxide films primarily composed of MgO, Gd2O3, and a small amount of CeO2 on the surface of Mg–3.5Gd–0.2Ce and Mg–3.5Gd–0.4Ce alloys. These compact oxide films can prevent the matrix from experiencing further oxidation. The deteriorated oxidation resistances of Mg–3.5Gd–0.7Ce and Mg–3.5Gd–1Ce alloys were found to be due to the severe internal oxidation caused by the distributed Mg12Ce phases along the grain boundaries.

High-performance multifunctional polyvinyl alcohol/starch based active packaging films compatibilized with bioinspired polydopamine nanoparticles

Bioinspired polydopamine (PDA) nanoparticles were synthesized and explored as functional compatibilizers in polyvinyl alcohol/starch (PVA/ST) matrix to develop high-performance multifunctional packaging film. The effect of the addition of PDA on the microstructural, mechanical, thermal, water vapor barrier, ultraviolet (UV)/high-energy blue light (HEBL) blocking, thermal insulating and antioxidant properties of PVA/ST composite films was fully investigated. Results demonstrated that the added PDA nanoparticles were evenly dispersed in the PVA/ST matrix, providing compact and dense nanocomposite films due to their compatibilization effect. Compared with virgin PVA/ST film, the resulting PVA/ST/PDA nanocomposite films exhibited greatly improved tensile strength, toughness, thermal stability, and water vapor barrier ability. Furthermore, the presence of PDA endowed PVA/ST composite film with excellent UV/HEBL blocking, thermal insulating as well as antioxidant functions. Thus, such high-performance multifunctional nanocomposite films hold the potential of protecting food quality against photothermal oxidative deterioration and extend food shelf life.

Tuning the microstructure for superb corrosion resistance in eutectic high entropy alloy

In this work, we demonstrate that the corrosion resistance of the FeCrNiCoNb0.5 eutectic high entropy alloy (EHEA) can be tuned by controlling the size of its eutectic structure. Through microstructure refinement, the EHEA exhibits a superb corrosion resistance in 1 M NaCl in terms of a very low corrosion current density and an ultra-high transpassviation potential, which outperforms a variety of other HEAs and conventional metals and alloys. At the fundamental level, the microstructure refinement results in a rapid formation of a thick and compact passive film with less Cl− adsorption on the EHEA, which results in significant enhancement in its corrosion resistance. The outcome of our research provides important insights into the design of corrosion resistant chemically complex alloys.

Compact Ga2O3 Thin Films Deposited by Plasma Enhanced Atomic Layer Deposition at Low Temperature.

Amorphous Gallium oxide (Ga2O3) thin films were grown by plasma-enhanced atomic layer deposition using O2 plasma as reactant and trimethylgallium as a gallium source. The growth rate of the Ga2O3 films was about 0.6 Å/cycle and was acquired at a temperature ranging from 80 to 250 °C. The investigation of transmittance and the adsorption edge of Ga2O3 films prepared on sapphire substrates showed that the band gap energy gradually decreases from 5.04 to 4.76 eV with the increasing temperature. X-ray photoelectron spectroscopy (XPS) analysis indicated that all the Ga2O3 thin films showed a good stoichiometric ratio, and the atomic ratio of Ga/O was close to 0.7. According to XPS analysis, the proportion of Ga3+ and lattice oxygen increases with the increase in temperature resulting in denser films. By analyzing the film density from X-ray reflectivity and by a refractive index curve, it was found that the higher temperature, the denser the film. Atomic force microscopic analysis showed that the surface roughness values increased from 0.091 to 0.187 nm with the increasing substrate temperature. X-ray diffraction and transmission electron microscopy investigation showed that Ga2O3 films grown at temperatures from 80 to 200 °C were amorphous, and the Ga2O3 film grown at 250 °C was slightly crystalline with some nanocrystalline structures.

Charged Exciton Formation in Compact Polycrystalline Perovskite Thin Films

Charged Exciton Formation in Compact Polycrystalline Perovskite Thin Films

A Facile Centrifuge Coating Method for High-Performance CsPbBr3 Compact and Crack-Free Nanocrystal Thin Film Photodetector

All-inorganic perovskite quantum dots (QDs), a promising semiconductor material, is suitable for new generation optoelectronic application. While there are many kinds of coating procedures for producing perovskite QDs peorovskite film, those methods require post-treatments and an additional dispersion support agent while still retaining pinholes and cracks. In this work, we report a facile method to produce CsPbBr3 film on a pre-patterned Pt electrode using a centrifuge coating method for photodetector (PD) application. Compact and crack-free films with ~500 nm thick from various particle sizes of 8 nm, 12 nm, and >30 nm were achieved with a suitable ratio of toluene/ethyl acetate solvent for visible light photodetector application. The optimized device has an on/off ratio of 103, detectivity of 3 × 1012 Jones, and responsivity of 6 A/W. In comparison, the on/off ratio of the device fabricated by the centrifuge coating method was 102 times higher than by the drop-coating method. The PD performance exhibited considerable moisture stability at mild high ambient temperature with no encapsulation for more than two weeks. The results suggest that this is a potential method for fabricating all inorganic perovskite nano-semiconductor films for further optoelectronic application in photodetectors, LEDs, and solar cells.

Tuning microstructure and improving the corrosion resistance of Ti-6Al-3Nb-2Zr-1Mo alloy using the electron beam freeform fabrication

Herein, the microstructure and corrosion behavior of Ti-6Al-3Nb-2Zr-1Mo alloy manufactured by the electron beam freeform fabrication (EBF3) have been thoroughly investigated. The evident prior-β grain boundary, the inside of which is composed of predominant α-lath and slight β-phase, is achieved. The EBF3-manufactured alloy displays a significantly improved corrosion resistance compared to the wrought alloy, especially the XY-plane. The X-ray photoelectron spectroscopy results reveal the formation of a more stable oxide film for the EBF3-manufactured alloy due to a higher fraction of phase boundaries induced by the fine α-laths; besides, the heterogeneous distribution of compositions between α- and β-phases can be effectively alleviated, resulting in the absence of the strong galvanic corrosion, which has been illustrated combined experiments and ab-initio calculations. The electrochemical analyses indicate that all samples exposed to the artificial seawater exhibit a typical spontaneous passive behavior, deriving from the presence of a compact oxide film, while a active–passive transition behavior is observed in 5 M HCl, stemming from the formation of a non-protective porous oxide film, which is well interpreted using the mixed potential theory. In addition, the oxygen reduction reaction, determined by diffusion and charge-transfer processes, is the predominant cathodic reaction in the artificial seawater, whereas, in 5 M HCl, the cathodic reaction is primarily associated with the hydrogen evolution reaction controlled by the discharge step.

Formulation Development and Pharmaceutical Evaluation of Lysiphyllum strychnifolium Topical Patches for Their Anti-inflammatory Potential.

Topical drug delivery systems are interesting and popular dosage forms for formulation development. Thai herbs are used in alternative medicine to treat patients suffering from severe illnesses. They have significant economic and cultural value in Thailand. This work prepared Thai herbal topical patches of Lysiphyllum strychnifolium stem extracts using pectin and Eudragit® NM 30D, and glycerin as a plasticizer. Astilbin was selected as a chemical marker in L. strychnifolium stem extracts. The L. strychnifolium stem extracts showed a statistically significant decrease in nitrate accumulation. The various properties of Thai herbal topical patches were not significantly different from blank patches. However, the trends of the properties depended on the amount of Eudragit® NM 30D. All ingredients were homogeneously mixed in Thai herbal topical patches and showed a smooth and compact film. The astilbin content was found in a range of 52.72-63.36 μg/cm2. The in vitro release of astilbin depended on the amount of Eudragit® NM 30D. The kinetics of astilbin release were fitted to the Korsmeyer-Peppas model. The astilbin showed low permeation; thus, polyethylene glycol 400 was used as a permeation enhancer. Polyethylene glycol 400 could increase the permeation rates of astilbin and the cumulative amount of astilbin in pig skin. This would be suitable for preparing the Thai herbal topical patches and could be developed for pharmaceutical and herbal products.

The structure and optical properties of amorphous thin films along the [formula omitted] - [formula omitted] tie-line prepared by spin-coating

The extremely high melting point of Mo, W and their sulfides acts as a barrier to the synthesis of chalcogenide glasses modified with these transition metal elements. Here, we demonstrate the preparation of amorphous thin films along the pseudobinary As40S60 - MoS3 tie-line by spin-coating. Using 0.02 M stock solutions, the limiting As40S60 : MoS3 molar ratio was found to be 1 : 3 for the deposition of highly transparent, very smooth and compact defect-free amorphous thin films. The spectral analysis of optical constants revealed that both the refractive index and extinction coefficient decrease with increasing MoS3 content. On the other hand, the contribution of absorption tails was observed starting from the ratio 2 : 1 and they gradually become more intense and red-shifted with increasing MoS3. Using Raman and infrared spectroscopies (ATR), we confirmed that As40S60 and MoS3 reacted chemically in solution and all thin layers contained only residual amounts of organic ammonium salts after annealing at 200∘C. Our results demonstrate that the sol-gel method can be a feasible and cost-effective strategy for the preparation of amorphous chalcogenide thin films containing transition metals.

Synergistic inhibition properties and microstructures of self-assembled imidazoline and phosphate ester mixture for carbon steel corrosion in the CO2 brine solution

The synergistic effect of oleic imidazoline (OIM) and alkyl phosphate ester (APE) for corrosion inhibition of carbon steel in CO2-saturated brine solution was investigated by electrochemistry and weight loss measurements. The effectiveness of corrosion inhibition is correlated to their relative compact film of OIM and APE adsorbed on metal, which is further correlated to the self-assembled structure in solution and the adhesion parameters on the surface. The optimal ratio of OIM and APE for synergistic corrosion inhibition is equal to one. The adsorption of mixed inhibitors on the metal follows the Langmuir isotherm. OIM and APE with dominant hexagonal liquid crystals (H1) in the solution correlate to the incompact monolayer and bilayer on the steel surface. OIM/APE mixed corrosion inhibitor forms catanionic complexes with lamellar structure in solution, which correlates to compact film coverage on the metal surface and corrosion inhibition. The mechanism is further studied and correlated with their critical micelle concentration (CMC), surface tension, contact angle(θ), adhesion tension, and adhesion work (WA) in diluted solution and on the metal surface. The studies demonstrate that a correlation of corrosion inhibition to the self-assembly structure in solution and on the surface exists when the mixed surfactants are used as corrosion inhibitors.